It went free to play.
...and became horrendously worse than it was before.
Steam was practically giving away STO accounts on month before the F2P so I nabbed a copy for like 2 bucks. I got my character to level 50 (max level) in 10 days.
I'll give you a quick review:
Pre F2P the game was Star Trek. Science ships did science and 'trek' things, Escorts were kings of damage but died rather easily, cruisers could take gobs of damage and keep fighting. The ship skills and modules were very star trek themed and it was complex enough that you really had to think where to put your skills so your ship could do really cool stuff. Due to the complexity there was a vast variety of skill templates people used and some players were renowned for being damn good at X thing ..which made the guys good at Y thing nervous and the guys good at Z thing had a field day since they were the natural enemies of X. In short, you never knew just what you were up against or what your team-mates could do and finding out was awesome.
Post F2P brought about a patch that took away all that complexity and trek-ness and turned it into a stupid-proof , cookie cutter game. Everyone has access to all skills and most skills were dumbed down in requirement and effect so that science ship abilities do nothing anymore, cruisers cant really take more damage than other ships and escorts became king since the dumb masses the game was patched for LIKE explosions and laser beams all over the screen..so weapons became the dominant, easy access, no thought required ship.
Klingon faction, which had the most varied and unique ships has been consistently nerfed to match the cookie cutter federation ships. The latest casualty were the carriers... they nerfed the fighter pets in damage and AI so that they are nothing more than useless little things and the carrier relies now on its own ship-borne guns to fight. Its like the fighter pets are now nothing more than decoration.
...and the future holds worse things. The devs have already stated that they will continue releasing 'unique' ships via scam-method lottery (players pay real money for a 'key' so they can open 'treasure boxes' that drop from virtually any NPC) which make any of the no-real-life-money cost ships look wimpy and the 'store' ships (ships you pay for with real life money to have in game) are also constantly being nerfed and made obsolete by the constant new arrival of scam-lottery ships.
That is, the few store ships that are still nominally useful. Most of them were pre-F2P ships so all the skill and ship stat nerfs that put into the game when it was dumbed down turned them into weaker copies of free ships.
That company has no idea what its doing anymore. Every patch they break a core element of the game and take a month to try and fix it (with worse results). I think the original game devs are no longer working on STO.. they've got life-support devs apparently working half time on that game and they will simply keep milking that cow until it flops dead.
..the PWE way.