I posted the following in a different thread, but since it seems to fit:

Quite true, high level and low level D&D play are not the same.
Recently this Forum has had threads by those who don't like high levels:
Why do almost all editions of D&D fall apart around 10th level
Those who like high level "Naruto/Wuxia"" style adventures, and prefer 3.5 because of that:
Sell me on 5th edition
And those that simply hate low levels
Roleplaying level one
I think it's a strength that D&D can accommodate different power levels, but if players & DM's enjoy those different levels is another matter.
While going "Dragonslaying" has appeal, I (for example) usually retire PC''s at around 5th level, others may start at even higher levels. To each their own, but it may be a more noticible problem now because (at least with 5e) PC's level up much faster than they used to! This makes the transition from low to high levels harder to acclimate to. IIRC it used to take at least three times as much "table-time" to "level up", as it used to. But don't just take my word for it, let's see what a co-creator of D&D wrote about level progression:
Quote Originally Posted by April 1976 issue of the Strategic Review


D&D IS ONLY AS

GOOD AS THE DM

by Gary Gygax


Successful play of D & D is a blend of desire, skill and luck. Desire is often
initiated by actually participating in a game. It is absolutely a reflection of the
referee’s ability to maintain an interesting and challenging game. Skill is a blend
of knowledge of the rules and game background as applied to the particular game
circumstances favored by the referee. Memory or recall is often a skill function.
Luck is the least important of the three, but it is a factor in successful play
nonetheless. Using the above criteria it would seem that players who have attained
a score or more of levels in their respective campaigns are successful indeed. This
is generally quite untrue. Usually such meteoric rise simply reflects an in-
competent Dungeonmaster.
While adventurers in a D & D campaign must grade their play to their
referee, it is also incumbent upon the Dungeonmaster to suit his campaign to the
participants. This interaction is absolutely necessary if the campaign is to con-
tinue to be of interest to all parties. It is often a temptation to the referee to turn
his dungeons into a veritable gift shoppe of magical goodies, ripe for plucking by
his players. Similarly, by a bit of fudging, outdoor expeditions become trips to the
welfare department for heaps of loot. Monsters exist for the slaying of the ad-
venturers — whether of the sort who “guard” treasure, or of the wandering
variety. Experience points are heaped upon the undeserving heads of players,
levels accumulate like dead leaves in autumn, and if players with standings in the
20’s, 30’s and 40’s of levels do not become bored, they typically become filled with
an entirely false sense of accomplishment, they are puffed up with hubris. As they
have not really earned their standings, and their actual ability has no reflection on
their campaign level, they are easily deflated (killed) in a game which demands
competence in proportionate measure to players’ levels.
It is, therefore, time that referees reconsider their judging. First, is magic ac-
tually quite scarce in your dungeons? It should be! Likewise, treasures should be
proportionate both to the levels of the dungeon and the monsters guarding them.
Second, absolute disinterest must be exercised by the Dungeonmaster, and if a
favorite player stupidly puts himself into a situation where he is about to be killed,
let the dice tell the story and KILL him. This is not to say that you should never
temper chance with a bit of “Divine Intervention,” but helping players should be a
rare act on the referee’s part, and the action should only be taken when fate seems
to have unjustly condemned an otherwise good player, and then not in every cir-
cumstance should the referee intervene. Third, create personas for the inhabitants
of your dungeon — if they are intelligent they would act cleverly to preserve them-
selves and slay intruding expeditions out to do them in and steal their treasures.
The same is true for wandering monsters. Fourth, there should be some high-level,
very tricky and clever chaps in the nearest inhabitation to the dungeon, folks who
skin adventures out of their wealth just as prospectors were generally fleeced for
their gold in the Old West. When the campaign turkies flock to town trying to buy
magical weapons, potions, scrolls, various other items of magical nature, get a
chum turned back to flesh, have a corpse resurrected, or whatever, make them pay
through their proverbial noses. For example, what would a player charge for like
items or services? Find out, add a good bit, and that is the cost you as referee will
make your personas charge. This will certainly be entertaining to you, and laying
little traps in addition will keep the players on their collective toes. After all,Dungeonmasters are entitled to a little fun too! Another point to remember is that
you should keep a strict account of time. The wizard who spends six months
writing scrolls and enchanting items is OUT of the campaign for six months, he
cannot play during these six game months, and if the time system is anywhere
reflective of the proper scale that means a period of actual time in the neigh-
borhood of three months. That will pretty well eliminate all that sort of
foolishness. Ingredients for scroll writing and potion making should also be
stipulated (we will treat this in an upcoming issue of SR or in a D & D supplement
as it should be dealt with at length) so that it is no easy task to prepare scrolls or
duplicate potions.
When players no longer have reams of goodies at their fingertips they must
use their abilities instead, and as you will have made your dungeons and wilder-
nesses far more difficult and demanding, it will require considerable skill,
imagination, and intellectual exercise to actually gain from the course of an ad-
venture. Furthermore, when magic is rare it is valuable, and only if it is scarce
will there be real interest in seeking it. When it is difficult to survive, a long
process to gain levels, when there are many desired items of magical nature to seek
for, then a campaign is interesting and challenging. Think about how much fun it
is to have something handed to you on a silver platter — nice once in a while but
unappreciated when it becomes common occurrence. This analogy applies to ex-
perience and treasure in the D & D campaign.
It requires no careful study to determine that D & D is aimed at progression
which is geared to the approach noted above. There are no monsters to challenge
the capabilities of 30th level lords, 40th level patriarchs, and so on. Now I know of
the games played at CalTech where the rules have been expanded and changed to
reflect incredibly high levels, comic book characters and spells, and so on. Okay.
Different strokes for different folks, but that is not D & D. While D & D is pretty
flexible, that sort of thing stretches it too far, and the boys out there are playing
something entirely different — perhaps their own name “Dungeons & Beavers,”
tells it best. It is reasonable to calculate that if a fair player takes part in 50 to 75
games in the course of a year he should acquire sufficient experience points to
make him about 9th to 11th level, assuming that he manages to survive all that
play. The acquisition of successively higher levels will be proportionate to enhanced
power and the number of experience points necessary to attain them, so another
year of play will by no means mean a doubling of levels but rather the addition of
perhaps two or three levels. Using this gauge, it should take four or five years to
see 20th level. As BLACKMOOR is the only campaign with a life of five years, and
GREYHAWK with a life of four is the second longest running campaign, the most
able adventurers should not yet have attained 20th level except in the two named
campaigns. To my certain knowledge no player in either BLACKMOOR or
GREYHAWK has risen above 14th level.
By requiring players to work for experience, to earn their treasure, means that
the opportunity to retain interest will remain. It will also mean that the rules will
fit the existing situation, a dragon, balrog, or whatever will be a fearsome
challenge rather than a pushover. It is still up to the Dungeonmaster to make the
campaign really interesting to his players by adding imaginative touches, through
exertion to develop background and detailed data regarding the campaign, and to
make certain that there is always something new and exciting to learn about or
acquire. It will, however, be an easier task. So if a 33rd level wizard reflects a
poorly managed campaign, a continuing mortality rate of 50% per expedition
generally reflects over-reaction and likewise a poorly managed campaign. It is
unreasonable to place three blue dragons on the first dungeon level, just as
unreasonable as it is to allow a 10th level fighter to rampage through the upper
levels of a dungeon rousting kobolds and giant rats to gain easy loot and ex-
perience. When you tighten up your refereeing be careful not to go too far the other way.