Retooling classes is a core part of Legion, no spec is left untouched in one way or another and some are completely different like say Survival Hunter is now for real the melee spec it pretended to be in vanilla, their artifact weapon is a spear and everything. Combat Rogue was changed into Outlaw Rogue and has a bandit/pirate theme, Demo Warlock is more of a traditional summoner now, Shadow Priest is all old god themed and has a void form where you try to stay in it as long as possible to do more damage, etc. etc. There are a ton of changes.
And yeah there is much less bloat. They've outright removed some abilities but I'd say a big thing is that talents tend to dictate your core rotation a lot more now. Most rows have a passive option that modifies your skills in some way or an active option that gives you a new button to push, and each spec has its own pvp talent tree separate from the pve one with similar options (though the skills you gain from the pvp talent tree can only be used in pvp situations).
Also it's not really about gameplay exactly but new animations are a big part of stuff as well, every melee spec has animations as good as Monk animations now. The thing I've noticed playing a lot on the beta is that it is very easy to tell what ability people are using just based on the attack animation. Makes watching the game more interesting.