Quests-
Honestly, I thought ESO's quests were better than Skyrim's. There are so many stupid radiant quests in Skyrim. I'm having trouble thinking of quests are aren't radiant quests, or worse. Remember all those stupid collecting quests, like fire salts, and all those ingredients for the Blackbriar girl? Or the fetch quests, that literally sent you to a random bandit cave. So dumb. Every Eso quest has a good story with real events that make you feel like a hero. Much better.
I guess if you consider the major quest lines in Skyrim, like the Companions, I start seeing your point some. But the quests in Skyrim did have more time to develop themselves, and less need to fit within a speedy mold. They had time to breathe and let you think. Here, you get a lot of information quickly. In three or so screens, they need to introduce who they are, what the problem is, and why you should care. Too many screens and you upset the speedy players.
Graphics-
I have no issues with the graphics. They stand toe to toe to my modded Skyrim game. But, I'm not too preoccupied with graphic quality in my games as much as other players are, so I'll drop this topic.
Mods-
Fairly certain they did take a look at the popular mods at the time, but you have to remember they started development 6 years ago, right after Skyrim. So they had maybe a year or two of mods to pull ideas from. I bet they borrowed a few ideas from Moonpath to Elsweyr though, as that was an early mod. Their boats come to mind as being simular. As for the sound mod you mentioned, not everyone wants realistic sounds. Realistic bow sounds aren't that loud for example.I prefer the loud fwip, as it feels like I'm really doing damage.As for AI, they could stand to be smarter in some occasions, but we also need them to have critia that wasn't in Skyrim, such as giving up their fighting if they wander too far. MMO vs singleplayer design here.
Gameplay-
Why? How come it has to be like Skyrim? It can be different. In vanilla Skyrim, you couldn't dodge roll. That doesn't make it a bad game. Likewise, the gameplay here is more casual. That's fine. Some people like mmos for their casual not stressful gameplay. Yes, the firsts in Skyrim are more real, more grounded. But I couldn't do that here. It'd be too much.
Also, fun difference. You know how in Eso, you start the game and don't spend too much time figuring out what to start doing? Go feed your horse or craft stuff, until you're ready to do some questing, right? I don't even want to start up Skyrim just because when I do, I'll spend 10 frustrating minutes trying to decide on what to do every start up in Skyrim. It's pretty bad.