What a nice inversion of the concept of the MMORPG genre. You succeeded there on so many levels. I don't want to post spoilers so I rather don't post a list here.
Imo all that's missing is a nice inversion to the pay to win concept. Shame I can not come up with a good suggestion right now.
I also couldn't come up with a good way to win the last boss battle. This was also due to the fact that the game became very laggy on the clickedy click bit. Could I suggest maybe that there should be a strategy to click only on certain power ups, while others maybe add armour and regeneration to the boss? So basically it's unwinnable when you just try to wildly click on everything that's flying by? Would be nice if you had to figure out which power ups are the ones that actually do damage (and then do damage maybe a bit more quickly).
If there was anything like that I wasn't able to work it out.