Smash Bros. shows us why it's bad not to have an achievement/ranking system of some kind.

[Platina]

The question is, will it solve fixing this issue?

I haven't nearly played Smash as much as I have with Splatoon and I've seen plenty of times where level 50s go trolling around in Splatoon. I've joined them a few times too because it's pretty amusing, but even with a level and reward system, it's not really fixed as it depends on the player.. though trolling is not a common occurrence, that is for sure

Rather, I think the main issue is that the 4 for all fight system is flawed to begin with.. because staying alive is best so not engaging in combat can help you win :/