While this hasn't been much of an issue, who is actually saying that 5e is badly designed or of bad quality?
I could see making that argument about this or that mechanic. The stealth rules are not well designed. They basically just washed their hands of it and told tables to sort it out. That's not quality design by any metric, regardless of how well someone might like it. You cannot claim quality for something that a thing does not possess. If the mechanics of a game are largely silent on how to resolve something, that's not a quality design.
Claiming that it is is just a rhetorical gambit to shut down conversation. "Oh, well, it's better to not design anything for that bit, because it is better to force DM's to play armchair game designers. Since I don't have any problems with it, you shouldn't either. If you do have any problems, it's just because you are such an inferior DM than me." is the basic message being conveyed.
And then sprinkle that liberally over any conversation that deals with trying to actually come up with mechanics for resolving whatever that bit is, and then double down by claiming that if people actually wanted those mechanics, 5e wouldn't sell as well as it does.
Did I miss anything? It's unbelievably self serving and 100% bad faith.