What drives a poor reputation for the Rogue class?

[Skrum]

It actually says "unfailing" before listing one fail state exception ("you can't") followed by another ("until.") Both of which are wide enough for the DM to drive an airship through. So no, it's not actually "can't fail."

Also - yet again, even if it is truly "unfailing" in your campaign, the question is whether what you gave up for that feature is worth it. By being an Assassin, you cannot also be a Soulknife or Arcane Trickster or Swashbuckler. All three of which have the same base class features that help with this, and stronger level 9 subclass features.

Agreed.

Thing is, if I'm just white-room contriving ways for this ability to be used, sure, I can think of uses for it. The character has a list of prepared aliases that they can swap from one to another, and thus no organization in the city can stop this character from infiltrating them. That's actually pretty cool, if it was a character in a book.

But in practice, I just don't see it working that way. For instance, if I was the DM and I was running a campaign that took place within high fantasy Gotham City and the entire game was about corrupt political organizations jockeying for power with violent crime syndicates, and the players were presented with the problem of collecting info from someone and they wanted to run an elaborate, weeks long heist involving disguises....like where would Infiltration Expertise fit in? If one of the players had the ability, would I say "perfect, not even going to make you roll, here's the info." Very plausible answer. What would I say if no one had the ability, but they wanted to do a heist anyway? In what two ways should I resolve it such that 1) Infiltration Expertise actually means something, and 2) while still encouraging creativity from the players (like what if one of them is playing a changeling eloquence bard?? Do I call for checks in excess of 23, just so they don't auto-pass? What if no one is playing a super-spy, and it's just the warlock riffing with Mask of Many Faces and a +9 Deception check?).

I just don't understand what slice of the game this ability is supposed to be about. Skills and their results have essentially no rules at all, so DM's are constantly making in the moment judgement calls about what they mean. Thus, many DMs default to "well, it should be possible for the players to do what they want because that's more fun and the game moves better, but it shouldn't be too easy either cause that's ALSO not fun," so the DC gets set at 6-12 points above whatever the modifier is of the rolling character. And then this ability, Infiltration Expertise, is written like Deception and Disguise Kits do X and Y and now with Infiltration Expertise you can do Z. But they're not written like that; nothing to do with the skill system is.