New EA App

I have a question to ask and it is a very important one where I want an answer concerning The Sims 4. I did not lose any dlc when switching from Origin to EA App, but I am worried about me making a new purchase on Steam or EA App because of the fact I originally purchased basegame from Steam instead of Origin or EA App. I wanted to stay on Origin as long as possible, but I was notified what I was using on Origin moved over to EA App where I could not use Origin anymore and if EA App is incompatible with Steam then "WHEN" will these two ever become compatible with each other and why did EA never think about making EA App and Steam "compatible" begin with? Do I have to switch The Sims 4 basegame and all of the dlc packs I purchased from Steam to EA App before I purchase a new dlc from The SIms 4 so that I can not only get newer dlc from The Sims 4, but also not lose any dlc as well that many people have complained about? If EA has not noticed any backlash yet about their new app, because of EA App and Steam not being compatible with each other (or at least not yet) I would be very surprised.