Whenever a game is free their is usually a catch and it nearly always takes the form of missing content from how it was published when it first came out So you have to make micro payments to get the full content.
Take for example microsoft flight simulator , 20 odd years ago when games cost £15 to £20 the sim was £50.
Several years ago it became free but with only 2 aircraft.
Their are a lot of games for free on epic but their is always a money carrot dangling in front of you , they show dlc's and other games in that series that you could buy to entice you into spending money.
The best free deal i got on epic was ... stubbs the zombie .... i had it on disc and just refused to work on windows 10. I even saw posting saying patches dont work. So imagine my surprise when the freebie worked , it did not crash and i completed it .... a good trip down memory lane.