That being said, it's motivating to see someone passionate trying to figure out everything about their character and sometimes that pays off and others, it doesn't. The dedicated players showed what Melee Jigglypuff and Brawl Sonic could do. Sure, they probably won't ever show the world that Sonic's number 1 or Jigglypuff is better than Melee Fox, but they showed us what those low tiers really are. Granted, it takes a lot of time and dedication, especially if it's a really technical character like Peach, Shulk, or Pac-Man.
As it stands, the bottom 5 are probably miles better than the bottom 5 of 64, Melee, and Brawl because of how this game was designed, the engine benefitting everyone more so than in previous games, and that it was balanced more and checked more than previous games. Hell, right now, a good player like say, Ally, could use Mario who people say is around mid-tier and still stand a chance against Zero's Diddy. Will Ally win? Maybe not, but it's not like seeing Mario get wrecked by Fox in Melee or watching Brawl Ganondorf do anything. That character design was a sin, dammit. No king of evil should feel helpless with that mutton chop and corn rows.
At the same time, the game's young and although there are tons more resources than in previous games where some player, let's say Joyce, is the best 64 Captain Falcon player in the world, but nobody knows. She might be stuck in Oregon slamming fools left and right while everyone thought Kirby was the best. The internet and the ability to stream and record gameplay wasn't there or wasn't sophisticated yet, but now it is. We can see how Luigi does, how Ike does, and how Mega Man does. Still, people will jump the gun. Remember how people cried that ZSS, Rosalina, Sheik, and now Diddy are OP? That was like what? 5 months into the game's life? I don't know about back then, but I think people didn't scream Fox was OP in Melee until a long time in comparison.
That leaves a lot of characters MIA because nobody plays them, nobody knows who plays them, and nobody is skilled enough yet to show people what they can do. Zero's Diddy is great, but imagine 3 years later. The amount of practice and MU experience would make his Diddy terrifying. That goes for any character, especially the current contenders for top 15. You thought you saw an awesome Greninja? Nah, wait a couple more years and that Greninja would make Ryu Hayabusa proud. Right now, the young water-frog has much to learn.