I think bounded accuracy works as desired. So no actual fans are not frustrated.
Plenty are. They talk about it on this very forum.
For a handful of examples:
Saving throws not scaling. (As I said, "bounded accuracy"
isn't actually about accuracy.) Plenty of people consider this a pretty serious hole in the rules, to the point that it's one of the most common house-rules in 5e to either give people more saving throw proficiencies, or outright making it so you get half proficiency to all non-proficient saving throws (effectively, "Jack of All (Saving) Throws.")
Monster HP inflation. (Again: not an
accuracy issue.) Lots of people complain about how 5e monsters are just huge bags of hit points you have to chew through and which don't really
do anything other than that. But that's, very literally,
exactly what WotC promised us when they proposed "bounded accuracy." They would give us monsters that scaled in difficulty primarily through how much HP they had and (to a lesser extent) how much damage they could deal, with little to no change in their hit rates and AC. That 5e monsters are kind of dull is a widely-held criticism
even by actual 5e fans.
The "training doesn't matter" problem, that is, skills feeling incredibly arbitrary. Because, with "bounded accuracy," skill bonuses start small and rarely become very large. A character with Expertise
and a maxed primary stat only gets +15, the maximum possible without magic items. That means they have a 20% chance to fail a DC20 check, something merely "hard," while a completely untrained rube with just a little bit of natural talent (say, +2 modifier) has a 15% chance to succeed at that very same task. The difference between the most talentless hack and the creme de la creme is only 16 points, and this cashes out as a shocking number of embarrassing failures and inexplicable successes. If 5e's designers had allowed more flexibility with their numbers and bonuses, this could have easily been avoided.
The flaws of the "magic items aren't required" claim. When AC is so static, sure, you don't "need" the items in the sense that they don't make the difference between being able to hit at all or not...but that was mostly not true in prior editions either, and 5e still has the "immune to non-magical weapons" thing so that aspect is false too. Instead, magic weapons become
incredibly sought after because they're practically the only way to improve your chance to hit....which makes DMs
even more miserly with items than they were before 5e, when it was supposed to be the "you can have items or not have items, it'll be fine either way!"
Bounded accuracy really did directly lead to a significant chunk of problems people complain about fairly regularly. These aren't one-off grumbles, they're commonly-encountered issues today, often requiring house-rule patches or strict DM policies to address. (And no, it is
not the case that the problem isn't a problem if you can house-rule it away. The Oberoni fallacy remains a fallacy.)