I really do wish ESO was a classless RPG. I tend to prefer those because they allow for a lot more creativity and a better match between the concept I have in my head and what I can do in the game.

For example, I once attempted to create an elementalist who used all four of the game's main elements - Fire, Shock, Ice. They were a Warden, so they had Ice covered from class and the other two I got from destruction staff and that skill line. It worked, but... it didn't. I ended up deleting her. Now, this character would have worked perfectly if I could have taken the Ice line from Warden, shock line from Sorcerer, and fire line from Dragonknight. But nope, that's not a thing.

The challenge with these kinds of systems, especially in a multiplayer game with some competitive elements, is balancing it. Personally I don't care that much about game balance provided it's generally reasonable, but others do get rather bent out of shape about the issue. Classless balance could have been done, but the game isn't going to shift to that so there my speculations end...