It actually is a real problem, and I have seen people complain in a real game. Claiming it's a meme is just incorrect.For as often as people online complain about the ranger, I have NEVER had someone in a real game complain and I almost always have at least one in the party. It's a meme, not a real problem.
The difference between online and offline complaining though is that most people offline aren't sitting around analyzing the class and that most people offline don't want to whinge/draw attention.
This isn't just true in 5E, or just in D&D, it's true in all TTRPGs, all editions of D&D.
Most players whose characters aren't very fun or effective just suffer in silence. What you see when their class is improved or whatever, though, is suddenly they're having a lot more fun and are more engaged with whatever area of the game their class was improved in. A smaller number do say things like "I wish my character was as good as X character" or express similar frustrations, but usually very briefly. Only a tiny number of relatively "serious" players actually work out exactly why their character sucks. Also a lot of those more serious players? They know which classes are weaker, and they just don't play them! How they gonna complain about a class they don't play? You don't complain about other people's characters!
Only when something is a truly amazingly awful situation like LFQW do complaints come to the fore from more "normal" players. And remember how loads of people used to say "LFQW isn't real!" or "I play at a table with martials and casters and no-one has a problem with LFQW!"? Even though it was obviously nonsense (and a lot of the time if you questioned people about it, it turned out they didn't actually have any martials, but they used to (funny that!), or they were playing only levels 1-5 or the like).