I fully understand your reasoning, and in the same way, I am not against mirrorless at all. I was in fairly early with the Sony A7RII, Canon Eos-R and Nikon Z7, and still use the A7RII.
But still to me, what you are describing are limitations that don't neccessarily prevent you from enjoying birding/wildlife photography and getting wonderful shots.
The limitation that mirrorless brings is more objectionable to me: lack of lenses that are not either top end inaffordable, or compromised consumer type in anything longer than 400mm.
I find that múch more constricting.
I can get a Sigma 500/4 for 6500,- a used 500E for the same, a 500PF for 4000,-
Such options are not available in mirrorless, and worse, appear to be nowhere on the horizon. Next to that, the crop high performance camera body segment has been obliterated with the transition to mirrorless.
In the light of that situation, I find the D500 a delight to shoot still. I guess I care more about the lenses in the end and a favorable cost/performance ratio. I keep my hopes up for e.g. a Canon 500mm f4DO or a Nikon 600mm f5.6PF or even a Sony 500mm f4, and a high end crop body, but am realistic enough to see that the market is polarizing into high end and low end.
Doug actually made some the points in his post I was going to make. And I agree, I can still do wildlife with DSLRs, no question, did it for years and thoroughly enjoy it. However, if I had spent all my life hammering nails with a wrench and someone offered me a hammer, that would quickly become my preferred tool
And while the difference between mirrorless and DSLRs isn't as striking as that of a hammer and wrench, there is a difference - at least between the current high-end mirrorless and DSLRs. For me, mirrorless makes it easier and does solve problems I've had with DSLRs. Of course, I had solutions to those problems with DSLRs, but mirrorless offered even better solutions. I'm confident in my ability to get the shot with any type of camera (mirrored or not) it's just that mirrorless makes it easier and allows me to concentrate on more artistic aspects of the image - and in some cases, the technology allows me to capture images that weren't was easy / possible with DSLRs.
One quick example of that is tracking. Last year I was photographing swallows - or trying to - with a D6. They were landing on a bridge and I'd focus on the bird and chase it as it took off. Despite the AF point being on the bird (GRP in this case, but I tried several others with equally bad luck) after a half an hour I had exactly zero keepers. Just for fun, I tried the a9ii and used its tracking mode and immediately started getting keepers. The a9ii had technology the D6 didn't and it allowed me to get a difficult shot. (Also, I have captured swallows with D5/6 and even D7500 series cameras under different conditions, it's just that this scenario stymied the D6).
Still, in the end when I'm out shooting, I really don't care what style of camera I'm using - as long as it's not holding me back, I'm a happy camper
As for lenses, it depends which mirrorless system. They are all still in their infancy and more lenses will come in time. As I mentioned in a recent video, if you're happy with your DSLR, now is a really good time to hold tight and see what happens. Good times ahead no matter what
(Oh, and I agree - there really is an extreme polarization starting to happen between low and high-end gear, although it's always sort of been there to a greater or lesser extent. - only recently did we get an "in-between" lens like the 500PF)