I don't understand why people complain about mass pawn promotion. The losing side is free to resign at any point. It's the player who is overwhelmingly winning who is forced to keep making moves.
That said, it is sometimes rude. The player who is first to treat the game as a joke (overtly not playing their best) is the one being rude. At lower ratings it's hard to tell if they're still trying their best when they don't resign in overwhelmingly lost positions, but sometimes they just don't understand, and when you promote a lot against a person like this you're the one being rude.
My motivation for this came from a game between Nakumara and a computer engine that lasted 300 moves before he pulled off a mate with 8 bishops. I can't post the game from my phone, but if someone would do that for me, I'd appreciate it.