If "advocating" means pestering the DM for advantage or trying to impress that "by RAW they are entitled to" whatever, no, they don't. Call me a tyrant...
Advocating means, in part, pushing the rules envelope for any advantages that might be hanging around. And I wouldn't call you a tyrant for pushing back against that advocation, I'd instead call you a DM who is doing his job.
Actually, we completely disagree here. If, as a DM, I say "no evil PC" (which is a common campaign restriction) and your PC willfully commits an atrocity, and as a DM I judge that it turns him evil and therefore an NPC, that specific character in that campaign becomes just that, an NPC, which I control as the DM. You can find yourself another character to play, or leave the campaign and recreate the PC somewhere else, but the real character is still part of the campaign, as a NPC.
If you as DM say "No evil PCs" I walk out.
Why?
Because you're telling me how to play my character, and that just doesn't fly. Further, because you're willing to tell me how to play my character in this aspect it's clear I can't trust that you won't - then or later - tell me how to play it in other aspects. (examples I've seen posted by others in this forum include no in-character romances, character must be of the player's gender, etc.)
Guidelines are fine. Hard rules are not; and the only way you-as-DM can turn my character into an NPC is if I willingly hand it over to you (and in my view this includes even if-when I-as-player have left an ongoing campaign; the character still belongs to me and you need my permission to do anything significant with it).
And maybe it's not one that, as a DM, I want to master, and especially not one that the other players want to have in their game. So it's fine, it's a new flow, but controlled by the DM.
If the other players don't want it that's one thing, but as a DM I've always seen it as my job to more or less run whatever the players put in front of me; and this can (and does!) include all kinds of left turns, unexpected actions, and plain ol' crazy ship.
Sure, at session 0 I'll make a few preferences very clear as to what I don't like DMing (usually revolving around players trying to turn the game into Economics 101 by becomeing businesspeople instead of adventurers), but if a character and-or class exists as playable within the setting I don't restrict what a player can do with it.
Actually no, I don't. This is why I love 5e and its "rulings over rules". When I create such a ruling, it's local and adapted to the circumstances. As I'm pretty sure that these exact circumstances will not happen again, I am free to rule again as I wish for the next set of circumstances, which will be different.
If game-element X works a certain way this time but a different way next time under similar circumstances, how are the players supposed to be able to make informed decisions?
I'm not even sure what you are referring to, but the Wheel of Time has a fairly consistent magical system, which actually follows fairly closely what happens at high level in campaigns, with PCs becoming powerful, then taking on responsibilities, then needing to abandon them for a time, etc. And the same thing with anti/counter magic thingie, which suddenly pops up to create obstacles, then becomes wielded by the characters, before some anti-anti-magic things pop up.
After that, while I agree that the middle books are quite slow, it's still one of the best sagas of the genre, and the final (Brandon Sanderson again) is absolutely epic.
Even though it had bogged down as you say, I found myself even more disappointed with it once Sanderson took the helm.