The basic primary gameplay is still the same. Many class's DPS rotations are actually not even changing significantly.
The changes include things like the removal of hit rating and making all attacks (generally) always land, not allowing flight in the new zone at all, even at max level, and designing the zones in such a way that this does not become a huge inconvenience, but also including things like jump puzzles and making use of vertical space in a way that wouldn't work if they allowed flying (but still designing the areas artistically such that flying could be added later with the flip of a switch). They've also removed systems like Reforging (which allowed you to transfer some of one undesired secondary stat into another more desired one), removed profession-specific stat bonuses completely (e.g. ring-only enchants for enchanters, and have made engineering toys available to all players but reduced their power), completely rethought stat customization systems like enchanting and gemming (enchants are now limited to a few slots, but give a massive amount of secondary stats, and you can choose any secondary stat in each of those slots rather than selecting from a limited number of stats per slot. Gem sockets are now randomly assigned to gear as a low chance "bonus roll" rather than being static, and are more powerful, and do not provide "primary" (AGI/STR/INT) stats).
All armor in the cloth/leather/mail/plate slots now automatically adjust between those primary stats based on your spec. So a paladin can use the same armor to heal, tank, or DPS. Neck/cloak/weapon/ring/trinket do not do this, and are still spec specific. There is only one tank-only stat (bonus armor) and one healer-only stat (spirit) and those stats only appear on those spec-specific accessory slots I mentioned. Set bonuses also automatically convert to match your current spec (so the same Tier 17 armor can be used to tank/heal/DPS for a paladin as I mentioned before, rather than having to gather 3 copies of the set).
A lot of these loot changes are based around the idea of being able to loot an item and immediately equip it instead of having to wait until after the raid and going back to town and going through the process of figuring out your new hit cap and completely regemming, reforging, and re-enchanting all of your gear.
Again, if your problem was with the basic combat, the changes probably aren't going to make you happy, They're mostly systems changes and stat customization changes.