Having had my first taste of mirrorless with Sony’s NEX 7, and now a more updated and thorough taste of it with my A7R IV, I can tell you that absolutely there is no way I would ever return to a DSLR. I love my mirrorless full-frame camera with its IBIS and its EVF and its various bells and whistles that all work just so very nicely for me....
I totally get it. I have 2 mirrorless cameras that are awesome. Wouldn’t trade them for anything! They’re the future, or a future, anyway.
But in keeping with the original post, again, there are zero compelling reasons to sell my d850. Why would I? It has world class AF, astonishing image quality that is the equal of any mirrorless system on the market (because it’s the sensor+glass+image science, not the mirror, of course), unbeatable glass, and a large, clear, bright OVF and feels perfect in my hands. I’d also certainly buy a DSLR - a D6, maybe used D5 - but there are other things to save for, like more yummy glass ?.
Don’t get me wrong. Mirrorless cameras are great. I love the Z bodies I’ve had the opportunity to shoot from friends. Some of the Z glass is hands down the highest quality I’ve seen and I may pull the trigger on a used Z6 for some video use cases for work. Oddly for me, I seem to have been bitten by the video bug. Maybe it’s all the crappy video conferences for work that made me start thinking about production value, who knows? But my d850 isn’t gonna fund it and I’ll wait until I save the dough. Why have fewer cameras when you can have more ?