I have some thoughts and opinions on some characters specifically that I want to mention
Bowser is actually decent. He feels extremely fast and he hits like a truck. He's probably the second best super-heavyweight in the game.
Bowser Jr. feels less clunky than the other low tiers, and I think he may not be dead last anymore after playing him a bit. He's got some stuff going for him (even if a lot of it is negated by his weaknesses) and I think that he may not be bottom 3 and even if he is still bottom 3, I can say with absolute certainty that there is at least 1 character worse than him.
Feels clunky. He feels like if Up-Air: the Character had his up-air removed and then got the rest of his moveset butchered even further. Despite his high speed, his movement still feels sluggish as well. Not to mention he's still combo food. He's most likely high mid tier at best.
The best super-heavywieght and may be a secret top tier pick. He feels really fast in all aspects and his unique moveset and attributes work very well against a lot of Ultimate's best characters. He still struggles with landing and against projectiles, but that's about it. With decent matchups against Marth, Lucina, Ike, Snake, Mewtwo, Luigi, and several other potential top tiers, He's going to be a big threat in Ultimate.
Underrated. He deals damage quicker than any other character in the game (except maybe Ganondorf) and kills incredibly early too. His recovery is still mediocure but is much better in comparison to the rest of the cast than it was previously. I feel like he is about as goo as his Melee counterpart and is actually better than Mario.
Ganondorf is a weird character. He's slow in movement, but his frame data is better than every other super-heavyweight except DK. This makes Ganondorf really oppressive against close range characters like Mario or slow characters like King Dedede but this also makes it so he struggles in many other matchups. He's probably a mid tier, though if people push him as a character, he could be high mid tier.
Link is overrated. His changes to bomb are cool, but actually seem to nerf him because if an opponent picks it up, Link can't use it or explode it which is worse than Smash 4 bombs which would explode, forcing the opponent to choose an option which was always punishable . The removal of his tether was also a nerf as his recovery is back to being poor again, similarly to his Brawl and Smash 64 incarnations. He also suffers from the same issues he always had. He's probably a mid tier.
Luigi is a top tier. His only weaknesses are his air speed and recovery, and he does have some mixups he can do do make his recovery a little better. He's essentially a better version of Sheik. While he lacks he movement speed, he actually deals damage, and is able to kill more effectively than her.
Mario has similar issues to Falcon and suffers from the same clunkyness. However, while Falcon struggles because all of his options were nerfed, Mario's best options were nerfed but his other things that wern't great, but were still good were reletivly untouched so he still has some things he can do, unlike Falcon. He's probably a low high tier but still a decent character overall.
Roy's the best sword character. If Chrom's recovery wasn't trash, Chrom would be the best sword character. Roy seems to be the best due to how much he benefits from the game's mechanics, along with his high speed and adaptability (although Chrom's adaptability is better than Chrom's).
This is the character that I can safely say is worse than Bowser Jr.. She is one of those characters who feels really clunky like Mario and Falcon. Not to mention, nothing in her kit is truly notable, and she also has issues killing due to the high lag and poor hitbox placements on all of her attacks. She also struggles against projectile characters, rushdown characters, and sword character, which is a lot of the characters in Ultimate. With all of these things going against her, she is truly the worst character in Ultimate in my opinion.