fmw
No longer a newbie, moving up!
Fast super-teles, high-end, fast mid-range zooms, fast portrait primes, good UWAs, and PC lenses.
You can adapt any of these to a mirrorless body with inexpensive adapters. The mirrorless cameras, so far, are designed for serious amateurs who don't use these kinds of lenses, not for pros. If I really need a PC lens, I can rent it and adapt it to my mirrorless bodies. Or I can even buy one and adapt it. I already have a Nikon to Fuji adapter that works just fine. No need to worry about extreme wide angles. Fuji already has them in the regular lineup. I assume the other manufacturers do also.
I moved to mirrorless to have a smaller, lighter system, not to use with fast super teles. It gets down to what you need. My guess is you don't need a mirrorless. Nothing wrong with that.