This is at least a lot more accurate than most of the erroneous beliefs about 4e repeated by people who obviously have a very poor understanding of what was possible in 4e, at least once the system had matured away from the PHB's overly careful and inexperienced "samey" power design and provided all the PHB class build variants with better tools for their intended jobs. And when it comes to 4e class features outside the standard AEDU system, I think it's worth keeping in mind that many of the classes found in the 4e PHB actually grew to become some of the most powerful in the game, despite the increased competition from several newer classes which had significantly better designed class powers right off the bat when they were released.
Nitpick: "Captain Cascade", as the highly optimized early TWF ranger build (by Lordduskblade) was sometimes jokingly called on WoTC's 4e Char-op forum, couldn't one-shot Orcus (CR 35) in early Paragon, nor in mid Paragon when he could grab the 15th level (Daily) Blade Cascade power which his signature overkill combo relied heavily upon. (IIRC, he also had to be redesigned to keep his Orcus one-shot capacity in Epic tier since the Blade Cascade power got nerfed in the very first round of errata released, and he was soon joined by builds of other "striker" classes just as capable of embarrassing the demonic God of Undeath in a similar fashion, such as the "Storm/Hurricane of Blades" barbarian which could achieve even greater DPR spikes during one or two rounds per encounter or day.)
While I believe this is probably a quite accurate description of the design policy for the 4e PHB, that policy obviously had a clearly noticeable effect only on the options found in that very first book. And I can't help but find it a bit amusing that the 3.5/PF standard fighter/wizard comparison translates so poorly into 4e, since both the fighter and the wizard were two of the strongest classes in the game, with the fighter having a potential the one-dimensional 3.5 namesake can only dream of and the wizard being a more powerful "controller" class than any other in 4e by a pretty wide margin.
I fully agree. It's the power level of individual spells and the daily limits being largely exclusive to casters which are the main culprits for the C/MD in 3.5/PF. The power of spells can of course easily be tuned down, but balancing classes primarily regulated through limited use abilities with classes primarily regulated through at-will abilities is impossible, at least if the game is also intended to allow for a varied number and/or makeup of encounters faced between instances restoring limited use abilities. In short, a single system simply cannot provide balance, limited use classes, unlimited use classes and a varied encounter pacing all at once. One or more of these goals must be given a lower priority in order for the other goals to be met.
And here's the "samey" myth again. Didn't play much 4e games using more than the PHB, and never with PCs using options like hybrid classing, did you?
If you had, your impression most likely would've been quite different. To give you a glimpse of just how much 4e classes and builds could differ, have a look at a couple of "Ultimate Defenders" like "Darth Vader" and the "Inexhaustible Dragon Sovereign". Then I suggest you ask yourself whether you believe any 4e class designed for another primary combat role could've been even remotely as good at protecting a party as either of these two are, how good the defenders in your 4e games were at their main job in combat in comparison, and whether you believe these "Ultimate Defenders" have mechanics and/or play-styles more "samey" than those of most single-classed PF martial builds.
I don't think this was a major reason for the failure of 4e, nor that too much was sacrificed to achieve balance when taking the entire system into account. That said, I believe the poor design of many options in the PHB (probably along with 4e's "striker" classes in general) is very much responsible for most of the bad impressions people have of 4e, including sacrificing too much to achieve balance, and for a lot of people giving up on the edition after having tried it out a bit early on when few or no additional player options existed.