Welcome to the community @cross.eyed.oni! 
Unfortunately, not all comics are able to be added to DCUI immediately due to a variety of reasons - however, we are regularly adding series to the platform. If you see that a comic series you’d like to read is not on DCUI, you can head on over to the thread below and submit a request for it to be added. The moderator team compiles these requests onto a list that we send over to the content team, who are in charge of deciding what gets uploaded to DCUI and when. Feel free to make any requests there! 
In the meantime, please don’t hesitate to let the moderator team know if you need anything! 