Server resets are a terrible idea. Most people don’t want their stuff deleted.
Now opening fresh new servers on a regular basis could be a great idea. Then start merging empty realms that are not part of the current “season”. No one loses their characters. No one ends up on totally dead servers.
And I don’t see why you couldn’t have some new servers with fun gimmicks, like having only one life (hardcore), or special world events, themes, and etc. Path of exile would be a good model for this. But it’s unnecessary.