Tier lists always assume equal skills of players. A tournament level player will always beat someone who is playing the game for the first time. A Diddy player will always beat a default Palutena player if they have equal skill and the match is fair (no hazards, no items etc.). Plus, look at the tournament results. Most people who've won big-level Smash 4 tournaments (like EVO) have used Diddy, Yoshi, Sheik, Rosalina, Falcon, Ness, or another high-tier character, while characters like Palutena, Zelda, and Wii Fit Trainer are rarely even seen in them. There's clearly a difference between the two sides.
Um, no, no they won't. Where do you get that kind of blanket ignorance from?
Sorry, but I don't think it matters a lick in the long run. The meta's still evolving, and if characters like default Palutena are low, it's because people have yet to realise their true potential. Tier lists only exacerbate that issue: high-tier characters are played because they're perceived as superior and have more of an established meta, while low-tier characters are left to languish for the opening round of the new game.
So no, a Diddy player will
not always beat a default Palutena, irrespective of skill level. That's a naive thing to say. The chances are mechanically and statistically weighed in Diddy's favour, that much is undeniable - but to present it as an objective fact is just absurd. I've seen many, many good Palutena players beat high-level players of all kinds, including Diddy. That they are not represented at national tournaments does not nullify their validity as competitive characters.
And for the record, I do think tier lists are a worthwhile pursuit, but I don't think they are the alpha / omega of the game's roster. It's too early to even cite tier lists as gospel truth - at least wait a while before making such bold proclamations without justifiable vindication to that end.