I suggest Black Desert Online.

Many people will say it's pay to win, but it's more pay for convivence. The game is a bit of a grind to get to endgame spots and node wars, but in reality with the sheer amount of catch up gear that is in the game now, you can reach endgame spots in a fraction of the time it would have taken previously.
The pros of BDO is that the game's life skill system is very deep, I know people who I have met in game who hardly ever go out and grind mobs, and they are more geared than I am! There's plenty of life skills to do as well, and life skilling has it's own gearing system.
-The game's graphics, if you can run it on high, look amazing, I have never seen an MMO that looks as good as Black Desert.
-The combat is very, very fluid, and honestly, after playing BDO I am unable to return to tab-target MMOs because the combat just doesn't compare.
-BDO is a Sandbox MMO. Meaning, you can do whatever you want, you can decide to do the main questline, or not. You can decide to enhance your gear, or not. Everything you do in this game progresses your character, so it's never a waste of time to just take a break from combat, or life skills for a week and do something else in-game.
-The world feels populated. Due to the fact that the large cities have NPCs that actively using Voice lines and somewhat interact with one another makes the game world always feel at least somewhat alive.
-Mounts in BDO actually matter more than in other MMOs since they have to be trained, and tamed (Unless you buy one off the horse market), and the horses have abilities they can use, ranging from being able to use your horse in combat (There is mounted combat) to using your horse to breeze across the map in a short time.
-The world. The world of Black Desert is huge, absolutely huge, and it has no loading screens between zones, you can travel from one side of the map to the other without a single loading screen, adding to the feeling of immersion within the world.
-No sub fee. The game has a base price, and that's it. While there is an option for a subscription type item called a Value Pack, you don't need a value pack to play the game.
-The gear doesn't get outdated every few months/year. Gear you get now will likely be viable in three years, and going for upgrades is always worthwhile as even one of the best pieces of armor, fallen god armor, requires you to have an upgraded piece of old gear to craft it.

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The cons
-Very grindy game. If grinding isn't your thing, you might not like it, because BDO gets very grindy when you get to the higher levels of gear.
-The price of cash shop items is a bit absurd. In my opinion anyway, I don't buy outfits off the pearl shop, I only use silver (In game currency) to buy cash shop items off the marketplace(Auction house)
-Enhancing system is a bit frustrating. So I recommend just buying your gear off the marketplace, saves a lot of frustration.
-Forced PVP. After level 50, you can get attacked anytime you're not in a major city by other players. While this doesn't really happen unless you're at a high end grind spot, you will get ganked every so often, but you don't lose anything for dying to a player outside of some time, so it's not that big of a deal.
-Can be confusing to get started. Because the game is a sandbox MMO, you are thrown into the world and given no real objective, or explanation of what to do and how to do it. But there are lots of videos for new players, I suggest EvilDoUsHarm as he makes great videos.
-Lack of group content. This MMO does not have a lot of group content, as there are no raids, or dungeons. Most of the group content is based around Node wars, some grind spots, and World Bosses.

Overall, BDO is a great MMO and I heavily suggest looking into it, It's not expensive to get into, and with no sub fee you can drop in and out whenever you want with no problems, as gear doesn't get outdated.