Star Trek Online the perfect MMORPG. It is Free to Play, but not Pay to Win. You may progress through the game faster, and get some exclusive items (mainly customization items) and features with a paid subscription, but the free version is still perfectly enjoyable.
The high-end ships and items are very expensive, but you do not have to pay with real-world currency just to purchase them. All you need to do is grind... a lot. I have almost one million energy credits, and that's all from playing casually, no gridning involved. You pick up items from fallen enemies, and if you pick up all of the loot critters and sell the stuff you don't need, you'll be rich in no time.
The more valuable currencies are a bit harder to come by, but again, they are obtainable by simply playing the game!
The game has a lot bugs, but almost all of them can be fixed with a console command, and I have only come accross one game-breaking bug. I feel like I should mention that I have put in alot of hours into this game. Like, hundreds (the 7.8 hours on record is only on Steam, I usually play with it's standalone launcher.)
And don't even get me started on the fan service! It's simply wonderful! Actors from the television series reprise their roles to voice their characters' in-game counterparts.
Whether you're a Trekkie, or just enjoy MMO's, definitely give this game a go.