Epic is clueless
1. No offline mode.
2. No mod support.
There used to be a fix for the first, but they "updated" the launcher to tie games to being online. Why would I buy a game from their store, if I can't access it whenever my internet connection is down due to isp problems/maintenance? Why would anybody?
This is basic goof-up's 101. Requiring persistent internet for single player games NEVER ends well.