For tripod work DSLR vs mirrorless may not really matter in general (assuming your DSLR and/or mirrorless have rear LCDs that can be tilted, which has been a game changer for me).
Mirrorless works better for me for non-tripod work. You don't have to mess with lens calibration if using AF--a good EVF is exponentially better than an OVF regarding focus if you are composing using a view finder and not Live View since focus is coming from what the sensor sees. For people pics, Sony's Eye AF beats the crap out of anything I can get with my Nikon D850 regardless of focus settings on the Nikon. Sony just nails it almost every time. Nikon, not so much. Much, much higher keeper rate related to sharpness with my son as the subject using my A7R3 compared to my D810 (or now D850).
Different tools with different strengths and weaknesses. But mirrorless (at least my Sony A7R3) has very real advantages compared to any of my Nikon DSLRs for some applications. On the other hand, there are things my Nikons can do better than my Sony. ISO 64 for landscape work is awesome and Sony doesn't have any TS lens options (though with the possible exception of the 19mm, Nikon isn't exactly class leading in the TS lens space...).
Your comment about weight is slightly off, at least regarding the A7R3. I've never gotten below 50% on a single battery with walk about shooting for a day or for shooting sessions of a particular scene even relying on Live View exclusively for the shoot.
On the other hand, once you factor in lenses the weight difference can vanish. 24-70 f/2.8 or 70-200 f/2.8 zooms are roughly equal regarding weight between Sony and Nikon. On the other hand, the Batis primes are quite light, have exceptional IQ, and have AF. Depending on focal length, Nikon primes are so-so performers and you need to turn to Zeiss (or Sigma) for really good IQ to match the sensor capabilities of the D850 (Art lens line for Sigma, Milvus or Otus line for Zeiss).
I'm not sure how I feel about a potential Nikon mirrorless. The rumors are stating that it will have F-mount compatibility, but after using my new D850 I've discovered that most of my older Nikon lenses just don't have acceptable IQ when used with a camera having a high resolution sensor--they weren't designed for that use and it shows. There are exceptions (and they are lenses that are either niche or focal lengths that I regularly shoot on a tripod) which made the D850 worthwhile for me. Depending on actual performance using an F-mount adapter, a Nikon mirrorless might make sense for me. Or depending on the IQ of the lenses released on the Z-mount. Will have to see.
my old Hassy has one focus point and a mirror box like a barn door but I still love it! The biggest benefit to mirrorless is the wysiwyg viewfinder (as long as you're not using flash) and how well it works with video. We'll see though I'm being open-minded.
