You would be surprised how difficult it is to balance a game such as Super Smash Bros. Many people do not know what it is like to actually try and balance a multiplayer video game. I do.
I own a video game, published on Steam, and am one of two primary developers who created just about every aspect of its design. We have about a dozen classes the user can choose from, the game is strictly multiplayer, and it does have pvp elements.
I spend so much of my time fixing bugs, trying to develop new content, and addressing other feedbacks from the community (such as major QoL issues, unfun or unintuitive mechanics, or requests for new minor features) that the balance between the various classes in the game often gets put on the back-burner.
We're just, honestly, so busy with everything else that it often gets to the point where we're like 'well, it isn't broke, let's not try and fix it,' and we leave balance in a state of 'good enough' perpetually.
Often, if we do try to release a balance patch, it leads to imbalances we didn't intend, makes other matchups worse in ways we didn't think of or recognize, or just all-around pisses players off. If somebody's 'main' gets nerfed, they scream bloody murder at us, threaten to quit, and leave us a bad review.
This is just a game with a dozen classes, where pvp is not the main focus (but part of many elements), with a playerbase of a few hundred on at any given time. I could not imagine the challenges of balancing an internationally-recognized roster that's 7x bigger than ours, on a game where the entire focus of it is pvp interaction, with actual, dedicated e-sport players and tourneys.
Right now, I'd describe Smash's state of balance as 'good enough.' They're probably afraid to make any major changes because of how big the repercussions can be. I could not imagine how hard it would be to test balance changes in smash prior to a patch release, given the kinds of insane techs, combos, and other stunts players manage to find in this game, many of which likely weren't actually intended by the game developers.
In the Ridley forums, he's a few frames away from having several really nasty combos, for example. Some of which are 0 to death, such as a triple fair train off the side of the stage and into the blast zone. All it'd take to break this character is to reduce the frame data on fair a bit, up his air speed a bit, reduce the knockback a bit on fair, or shrink its sweet-spot. Another really nasty one is plasma breath into his command grab. He barely can't do that right now as a true combo. A small buff to plasma's frame lag, his run speed, his instant dash speed, or the startup on his command grab, Space Pirate Rush, would give him a very nasty, true combo on this.
That's just Ridley. All these characters are likely like this. The interactions between them is so mind-bogglingly complex, one couldn't hope to redesign a character without seeing major shifts in balance, likely in unintended ways. You change, literally, one thing, and it can translate into all kinds of new things like 0 to death's, unfair true combos, or other forms of egregious game balance issues that are nearly impossible to find prior to releasing a patch and having high-caliber players lab it out for, sometimes, months on end.
I would not want to be the people who are responsible for balancing Smash Ultimate. I can tell you this. I bet they play the game a lot less than the people who play at the higher tiers of skill in this game, as they're too busy to get that good in the first place working on the game! Listening to the community can be very difficult too. What you often get are the loudest, most upset people screaming at you to do certain things that would upset the quiet majority. It's very difficult to come to forums or other internet gatherings to assess what actually needs to be changed to balance a video game, and most developers are so busy developing, they don't have time to play at a level where they can really understand and address the truest balance issues.
But, sorry for the long'ish rant. As for the OP, I love Ultimate. It's the first Smash game I've really gotten into, and find it to be a great way to socialize with friends and family. They did a great game on so many aspects of the game, and I can tell they put a whole lot of work into polishing it up. I'd give it a 10/10, and think it's one of the most balanced Smash games they've released (coming from the guy maining a low tier character, at that).