I think low tiers are drastically underrated. Part of that is because everyone assumes any good performances are due to matchup inexperience, and the other part of it is that the characters themselves are really underexplored. If you've been playing Melee for a couple years and main Fox, there's no shortage of examples to pull from to improve. You can learn what to do in any given situation just by watching the top Foxes and mostly just copying what they do. If you main Pikachu, you only have one good Pikachu player to learn from, and because Axe is so high level, he's probably not even dealing with the same issues a lower level Pikachu might deal with. If you main a character like Young Link, you basically have no role models to learn from and without a large group of peers to exchange ideas with, you will inevitably be making tons of inefficient and suboptimal decisions.
From a more general standpoint, I think it's kind of a shame more people don't play low tiers. I think the game is plenty fun with the 8-10 characters that are most common, but I feel like a lot of people don't really express themselves in game the same way they would if they played a less common character where they are forced to innovate more. The most painful example of this difference is when a player using an uncommon character decides to switch to Fox or another popular character, and they end up having the most generic and basic play style imaginable. They almost aren't even playing the game anymore, they're just doing a bunch of Fox things or Sheik things and they occasionally win because they're spamming good options.
The other reason this is a shame is because one reason people give for not playing low tiers is that they want to perform well. While I think it's certainly harder to get a grip on less popular characters because of the lack of footage/peers to discuss with, I think the effect character choice has on performance is overrated, especially at the local level. If you're not planning on putting in tons of work to become top 100, I don't know why you'd consider results when deciding your character. There's no tangible difference between being ranked 500th in the world with Fox or 600th in the world with Young Link. The simple fact that skill levels blend together by the time you're outside the top 100 basically makes it impossible to tell how high you're ranked in the first place.
Not picking a character because they are limited or frustrating or just not fun makes sense, but I think a lot of unpopular characters like Pikachu, Young Link, G&W, Mewtwo, etc. don't fit this description at all. They struggle in certain areas, but so do the top tiers. A new Falco main is going to be just as frustrated with getting gimped as a G&W main is with getting KOed early off the top. The big difference is the Falco believes he can learn ways to not get gimped whereas players who main low tiers (sometimes even TOP TIERS) are the first to blame their character for their loss.
Fox mains never blame their character and while you may argue that's because their character is the best, the effect of this mentality cannot be ignored. If you refuse to blame your character for your losses, then you're more likely to solve the actual problem. If you main Young Link or even a character as good as Samus/Peach, it's incredibly easy to blame your characters weaknesses for your loss and you don't look as hard for solutions or simply can't find them due to confirmation bias. Even low level Fox mains are insistent on learning to consistently ledgedash, which is by far the riskiest technique in the game, yet you look at Samus mains and they don't want to learn her aerial interrupt or Peach mains don't want to learn her variety of tricky airdodges/reverse ledgedashes to get off the ledge.