I want to start off by saying I do enjoy this games other aspects and I enjoy them however the combat system in ESO I cant particularly get into.
While I understand a lot of the combat changes made to traditional Elder Scrolls games comes from placing it within a MMORPG setting to me it does not feel as engaging as other MMO titles.
To me this is just because of slight things that have occurred while trying to keep the game feeling as traditional it can to the franchise but there is several reasons why this doesn't work.

Class Systems and Power Scaling
While classes are an integral part to MMOs to help define what your character can do, the issue comes later on when you look into building the spec of class itself, because of how power scales with spell power, weapon power, ect. "Play how you want" loses some value when it come towards "play how you feel like within the limited grounds" as some classes have little to no stamina morphs and have to fill this in with stamina based weapon abilities in order to flesh out their kit. This has resulted in hybrid classes not being optimal at all because having to share and disperse resource pools. The only Pseudo fix to this is the Pelinal's set, where I may have to give something else up to play how I want more optimally.
If power scaled of a singular stat instead of two it would make all forms of builds playable and more diverse builds making resources what they're intended to be; resource pools.

Skill Limitation
I'm somewhat under the impression this is a console based reason but the lack of skills that can be used feels horrible. While with weapon swaps it is 10 skills plus 2 ultimates with having only access to 5 at a time. To me weapon swapping feels clunky and detracts from the actual combat of the game. I feel like a larger skill pool per weapon would be a nicer start to add a bit of diversity to what can be had as currently for most classes regardless of if you're nightblade or necromancer, you run the same weapon based abilities and mages/fighters guild abilities as well as same gear, standing stone, consumables as every other class.
This also ties back into my argument about power scaling, there isn't enough stamina morphs for classes which means most classes end up all running the same thing. At least 75% of all class skills should have a magicka morph and a stamina morph to help promote skill diversity and potentially reduce the need to rely so heavily on weapon/guild based abilities.

Attack weaving
To me this is another horrible feature of the combat, yes resource generation is a thing but this having to weave, swap, use skills just feels more horrible the more latency you have due to having to be most effective with animation cancelling of items through weaving and having it to generate resources. I cannot think of another game that employs resource regeneration in this regard and rather takes me out of the combat having to then slow down and just click to then wait for a potion cooldown to maybe get into the real beef of it again. As silly as it sounds I would rather have the passive recoveries increased to make attack weaving still something within combat but not an integral part to sustainability of combat.

Tropes and skill tree suggestions - TES
This is more a cosmetic feel to why I don't like it:
Casting via staves; Can there be a cosmetic option to have it come out of your hands instead?
Sword and spell; It's no secret reading this my favourite trope is a spellsword, sword/wand and tome skill tree?
Unarmed skill tree
Spell power based swords and stamina based staves; this could also just be an outfit station change