Not sure if you're into this. But Warframe.
It's free, optional IAP to get stuff faster but not in a P2W way. Everything is possible to get free if you sink in time and/or be social and trade/sell stuff for premium currency so you still can buy stuff you want.
Game is loaded with content. Steep learning curve but when the game 'clicks' you're sucked in. There is a story that will make you go "wtf?" and that part is widely known as the "you completed the 30 hour tutorial. Now the game begins".
It's playable solo, recently added cross play which makes playing with others more easy and there are parts that are public where you can interact with everyone there. That makes it feel as an MMO.
The devs are active on Lemmy warframe@dormi.zone is the official Lemmy page since they moved from Reddit.