It doesn’t have open world PvP in the sense of WoW. PvP in GW2 has two forms:
What they call “PvP” which is somewhere between Battlegrounds and Arenas in design, and certainly instanced in the normal sense.
What they call WvW or WvWvW, which is open-world PvP but the world is separate from the main game world. It’s a huge area with castles and forts and baggage trains and so on, where large or small groups of players (or even soloers) roam and the players from three servers fight each other. It’s somewhat similar to DAoC’s RvR back in the day (better balanced but not as awesome as RvR). It tends to be marmite-y in reaction - i.e. people love it or hate it (and it’s not very predictable which).
Another option I overlooked is Elder Scrolls Online, which is still pretty alive, has decent graphics and plays in a decently modern way, so provides a WoW-type quality experience (which few MMOs do), but it takes a similar approach to WvW - there’s a gigantic area called Cyrodiil (yes that Cyrodiil if you play the TES games) with a number of zones where 3-Realm PvP takes place - you’ll be aligned with one of the realms and fight over castles and so on (again based on DAoC’s RvR, albeit even more directly as Matt Firor, once lead dev for DAoC, is in charge of ESO).
FFXIV is a thing too. Graphics and amount of content are WoW-ish, but… I dunno about you, but I was terminally unable to get into it, no matter how much I tried, and it’s not because it’s “anime” (I had a better time with BDO even). It’s just… painful. Ugh the mechanics. It highlights how tedious an MMO can be. And worse I think it only has fairly small-scale instanced PvP.