You realise things exist in smash games with little counter play?

Lil mac, arsene, waft, pikachu loops...

Luigi 0 to death is about the easiest thing to avoid by simply getitng hit by literally any move at 0 other than grab, and by the luigi inputting the complex tree against your DI.

Is it good game design? Probably not. But so are many other things. The point is, luigi isn't a top tier character, and this tech doesn't make him busted. That is all that was talked about in the original comment.

As for Plup. He's pretty good at melee, he's not that great at ultimate. there's nothing wrong with that.

MKleo and even samsora is a 100x more mechanically skilled than plup in ultimate. That isn't even debatable, and I guarantee you if you asked on stream, plup would agree with that statement.

Pushing buttons fast on your controller doesn't translate to actually being good at a game, which is evident by the fact not a single top melee pro can get top 10 in this game, let alone most not even getting top 50, top 100. Leffen grinded the game hard for a year and barely won a C-tier EU minor, and that's about it.