I could not recommend Guild Wars 2 enough.
If you're looking for an experience with numerous players, free exploration and the option to either soar through the game freely or grind the everlasting crap out of it, you can play this game any way you like.
There are a few components that require some grind, like raids and a part of the game called fractals (essentially a collection of mini dungeons that increase with difficulty the further you get into them), the rest of the game leaves you free to explore the world and pick off story elements as you level past a certain point.
PvP is available as SPvP, Structured PvP which allows two groups of 5 players to fight over points of interest on a map in order to acquire perks or straight up accrue points and win the maps, and WvW, which allows large groups from each of 3 servers to battle each other on massive maps to capture points, amass resources and outflank armies, or just ram down a few gates and capture a keep with some troops and some siege equipment.
The expansion also adds countless new elements into the mix, things called masteries, like the ability to glide and use mechanics like autoloot to pick up looted items automatically.
The community is very friendly, overall, with the only exceptions in some salty PvP matches, and occasionally raids, but that's understandable if they get their asses handed to them, all the time.
You also get to completely customize your look, with skins being just about the biggest thing in the game. Though, a lot of it is bought through the gemstore, but don't let that stop you, as gems can be bought with ingame gold, instead of actual money, if you choose.
New content is added regularly, and over the last year there have been several new maps and story bits introduced to the game. There are also indications that we are getting close to seeing another expansion, which would introduce the game to even more maps, story and mechanics.
If you want to try it out, the free version includes everything from the main game, with only a few limitations, but otherwise leaves you completely free to discover the world and meet other players, many of whom are happy to help out new players.
https://www.guildwars2.com/
Just one thing, if you decide to get the game, don't get it through a site like G2A, they're basically okay with trading in stolen merchandise, which leads to problems for developers.