Welcome to the Wario Forums, Kiwi! Don't worry about being a newer Wario fan, I only really got hooked on the greedy fatass in early 2024 because I played Wario Land 3 compulsively. Hope you have fun here, even if it's a bit quiet.
I'm not too sure on the canonicity being stated on DK's fight with Little Mac, but for Starfy, Wario appears for all the levels of a stage, helps you progress, and even teaches Starfy a new ability.
I mean, in the case of Punch Out and Starfy, the characters actually play a genuine role in what's happening. In Kirby Super Star, that one is literally just an easter egg and has no weight on the Dedede fight. Not really comparable in my opinion.