The major change overs were film to digital formats. I first used 8 x 10 film in the 1960's. Nothing came close in terms of resolution and dynamic range. I began to shoot pro images in the lab in digital format in 1990's, and would never go back to film. My current digital images are often in excess of 80 to 150 gigapixels (and more).
But for personal pix I continued to shoot film until the early 2000's. The immediacy of digital images was preferable, so I shifted. The ability to shoot hundreds of pix of birds in flight and throw away the (many) crummy images was economically undeniable. Mirrorless has helped improve that ratio, but the quality of the photographer is more important.
The era of DSLRs was initially limited in resolution and dynamic range. Not true any longer.
Resolution and internal image processing were consequent to improved chip design and digital processing advances.
The differences between DSLR and Mirrorless are reflected in weight, live view quality with improved EVF and representation of real time mods to shutter speed, aperture and ISO.
This is of variable importance, depending on subject material and where and how you shoot.
Overall, the market for stand-alone digital cameras has fallen by as much as 80%, regardless of whether you use DSLRs or Mirrorless, and depending on who you believe. Smartphones have captured the market, and there are many new generation talented photographers shooting very high quality images with the camera that is part of their smartphones.
I personally can't manage to hold my smartphone steady enough for good shots, and can't get decent photos of birds in flight with an iphone, but friends who have mastered flower and landscape pix on iPhone skill take superb photos.
I went mirrorless once EVF (electronic view finders) proved satisfying. But as my photo ambitions increased, I ending up with lenses that were so heavy that the difference in weight between Mirrorless and DSLR were insignificant.
You pays your money, and you takes your chance!

SLR like a film body? Probably only 1 or 2 new ones since 2000.

DSLR like a digital interchangeable lens camera with an internal mirror? Word is Canon will make no more EF lenses ending in 2020. We'll probably hear no more bodies with an announcement in 2021. Where the global market leader leads, others will likely follow.

It's widely rumored whenever a Sony mirrorless body is sold, another Nikon DSLR explodes into a cloud of dust. If you have any of these risky investments, keep them in ziplock bags to help contain the mess.