Some subgroups should be redefined

there's a really big difference in some classes in what specifies one as belonging to that particular class. some, like the juggernaut group, are pretty lax; you really only need to be immobile and melee to qualify. These guys were also the first sub-group to be named, and IMO they are the most "successful" in terms of diversity, as each one has their own unique reason to be picked and has many defining strengths/weaknesses that set them apart from each other

but then you have a very specific group, like divers. and it's not just "mobile melee fighter" or w/e. there are a lot of different requirements that make a champion defined as a diver. they need to be mobile, they need to have pick potential, and they need to be strong duelists. so you end up with the whole class as being this jumble of melee champions who all more or less have the same strength profile; they have enough single target lockdown that they can kill you or at least do heavy damage to you before you come out of CC, they usually make for decent-to-good initiators, they're usually good at taking down tanks and squishies alike thanks to in-built % damage, true damage, resist shredding etc. they're almost always burst-oriented but still able to DPS, and the biggest thing that separates them usually ends up being their items; the damage:tank ratio in their core builds, and their mobility; whether they use their dashes for juking attacks and outplays like Camille, or if their mobility is purely for leaping into the fight like Warwick. Olaf is the exception to this after he was moved to the diver group

Divers end up being a very 'generalist' class because they're a mish-mash of everything else. And to compound on that, a lot of them end up imitating each other, so when one is better than the rest, the rest aren't worth picking. The worst offenders of this in the past season are the usual suspects; who almost always push their peers out of the spotlight when they end up being dominant.

For groups like these, they need to have looser requirements, so that unique roles can be experimented with them; since riot moved Olaf into the 'diver' category, I expect that we might see more divers who have no hard CC lockdown or mobility , but I think more could be done in terms of unique strengths.

the subclasses I think fall into the same problem;

Vanguards - what should have just been defined as 'initiating tanks' has turned into 'initiating CC bots' and i would say that the recent class rework has only made them overlap more with each other. have become a very generalist class

Enchanters - mixed bag. They have a lot of overlap with their general mechanics, but they also have unique aspects individually that gives them power that other enchanters don't. their unique qualities should be made more prevalent and they would be much better off.

Marksmen - same problem as enchanters. Some of them are genuinely unique and offer different strengths; others just come in and out based on whether or not they can abuse a certain build. a lot of it boils down to sharing many strengths; they exist almost entirely to dump large amounts of damage on people, so the marksmen meta always revolves around either who can be most busted with either crit items or who can steal another class's items and use it better .

i think most other subgroups do pretty well in regards to niche. some have their generalists that tend to be problematic, but most of them have been/will be nerfed