Oh, there were a lot that could be cut. But as you say there were already 20 classes in the game. Also in the Essentials era classes I've either played or run for in Heroic tier and that were fun and couldn't be replaced with pre-4e classes without serious reworks for the player:
- Thief
- Slayer
- Knight
- Hexblade (currently one in the campaign I'm dropping in to)
- Scout
- Bladesinger (yes, really)
- Vampire
- Executioner (needed polish but there's a decent class there)
- Berserker (currently playing one)
- Elementalist
Yeah, basically the hexblade is the only true e-class that gets a solid thumbs up from me, and I don't see why we needed Essentials to have that, it could have just been a standard warlock build (which it almost is). The Vampire is not really an E-class at all, it is a standard class with just very few powers provided. And Elementalist definitely fills a niche, though I would have loved to have seen the sorcerer done as an Elemental class.
Not included includes the Witch, the Sha'ir, the Binder, the Blackguard (there could have been something there), the Skald, the Hunter (again an execution miss). The Crusader's very borderline. And I'm not sure whether there's anything to the Skald. Also the mage and the warpriest were pretty redundant and the Sentinel I've only ever seen once, and that for a dog-obsessed drop-in.
As I mentioned in my current campaign group there's an active hexblade and I've a berserker. The thing is that once you've filled out the basic classes then you have to experiment. Some of the best 3.5 stuff came from the experimenting.
but why even make more classes, there are tons of builds that were hinted in 4e but never provided, and many more that could have been.
Your experience is very different from mine

(The Esassin is a HoS class - but that book was the biggest mess in 4e)
HoS is a very solid book, except it has to dual use for both Essentials and classic, which is where it runs into some issues.
Blackguard was a good concept but HoS was a Mike Mearls project.
Blackguard is quite solid, but again it wasn't necessary to have Essentials to have that.
The Necromancer and the Nethermancer were both HoS subclasses and nicely fluffy. I've said before and I'll say again that one of the things where Essentials improved on base 4e is that evokers and necromancers are more inspiring than orb wizards and staff wizards.
But again, the problem with Necro/Nether is they are stuck being Mage subclasses, which serves no real purpose. I think that the different types of implement specialities are just as interesting, potentially as whatever is in Mage. It didn't get quite the focus I would have given it though. The summoner thing was a good start, with the tome. The IDEA of a more accurate wizard, a more potent effect wizard, and a more melee capable wizard (staff) were solid ideas though. I don't see the point of the change midstream to a different way of parsing it. Instead why not actually develop those themes? Necro could easily involve a new implement for instance, and Nether, meh, who asked for it?
Point. I really don't like the Artificer as it doesn't feel like it builds stuff - indeed I'd go so far as to say that it's the only time I actively prefer the 5e version of a class.
I don't know the 5e version. I found the 4e version rather fiddly, but thematically it is in a good space. Still, I agree I would have made it more focused on the crafting thing.
Yup. 5e's taken 4e's subclasses and run with the way it opens up design space right to the point of making the Psion a subclass of Sorcerer ("Abyssal Mind sorcerer"). It's made the decision for both good and ill to keep down the number of classes and instead do as much as possible with subclasses (putting a lot of what was done in 4e by both feats and powers there), and it's a choice I can respect.
I don't have an issue in some sense with it, but 5e's classes, that is 5e's PCs, overall are a lot less interesting IMHO than 4e's are. I like that it is a bit easier to achieve a specific concept, but there's not really enough leeway in there, and the lack of really interesting martial classes is quite telling.