1) They have terrible security (80 million accounts were exposed last week)
2) They have terrible customer service
3) Games are more expensive on Epic due to regional pricing
4) You can't play games offline
5) Limited social features
6) No screenshots
7) No controller support
8) They broke EU laws (and still do)
9) Scummy tactics (you had to tick a box to opt out of emails etc)
10) They are partially owned by Tencent (a company that sells user data to the Chinese government)
11) No achievements
12) No cloud saves
13) No game forums (many people went to steam for subnautica support)
14) Epic make you pay the transaction fee when purchasing games
15)They are anti-consumer (They pay for exclusive rights to games to try and force you to use their store)
16) They can refuse refunds even if you meet the criteria
17) No reviews
18) No Linux support