There's a huge difference with working what you've got and can't change and allowing team members to perform sub-par when they don't need to. I mean, I am fairly sure your guild wouldn't have tolerated people on a progress night to not have flasks/pots/runes/food...would they?
The talent change is like that - it will not change behaviour at all: people in raids outside of LFR will jump through whatever annoying little hoops there are to switch talents around, and outside of raids, except Mythic+, most people will pick a best all rounder off Icy Veins
Guilds don't usually minmax classes because they don't have them and having people level up and gear up multiple chars to raid level is far too onerous. They do however expect the team members to optimise their spec/class
It's entirely reasonable and expected in a guild, even in normal and heroic modes, to bring consumables and to pick suitable talents. Even to switch specialisation.
As has been endlessly pointed out the talent system in Legion is obviously built with switching in mind from the ground up. You don't take away baseline abilities and repeatedly put situational talents on the same tiers so that they mutually exclude each other without drawing that conclusion.
That's why deciding to put in extra hoops to jump through when people want to change talents after designing the talent system to more or less require them to change talents sucks.
We've already got plenty of "identity" in the classes. I think people in raids - the only place talents will really matter - care a hell of a lot more about maximising their contribution to the team effort and maximising performance than they do about thinking how great it is to be a single-target special snowflake
Playing affliction in AOE situations it was neve rmuch comfort thinking how great it was at single target. It just felt sucky to be rubbish at AOE.