It is true that dslr's are dinosaurs. It is also true that most of us are Nikon-centric even if some of us switched brands when Nikon was late with a top-of-the-line mirrorless. The problem seems to be that a Sony A1 ($7500) or Nikon Z-9 ($5500) are well over his $2500 budget whereas for $2500 a used D-500/300PF can be had. (A 1.4TC is another $500). What mirrorless setup in that range will produce better pictures?If you are now spending $2500 you are definitely in the ballpark to consider mirrorless. Good as they were all dslr cameras are on their way to being dinosaurs. We all want to push the camera we have, it's just human nature but it is not objective. This site is very nikon centric and mostly old folks like me who grew up on film slr cameras then reluctently adopted dslr cameras. But since you are starting out there is no reason to automatically buy into the old system or at least if you do do it with your eyes wide open and do your research as to the differences.
-Tom