It is not a huge loss though, because pros almost exclusively buy their DSLRs from Canon and Nikon.
I have to disagree about viewfinders and batteries being inferior. The viewfinder is an acquired taste. If you look at cinematography and movie production, you’d need to search for a long time before you found an optical viewfinder. And I just shot a 12hr production on a single battery, using the highest resolution DSLR on the market. No pro photographer will ever need more than a day of battery life.
I respectfully disagree with that. Current generation viewfinders have excellent resolution and very little lag, and while that will never be as perfect as an optical viewfinder, they do have the great benefit of being able to show you the image as it would be after exposure (so you can see which parts would be over or underexposed for example), and can overlay much more useful information.
Don't forget that EVF can surpass OVF in image quality because they can apply lens correction to the viewed image which brings the image closer to the final product. (although AFAIK it's not done currently)
Canon and Nikon are also shifting en masse to mirrorless. So the tides have clearly changes across the board.
I upgraded last year to a Sony A7ii, and this one's even better.
The tl;dr is that, at this point, optical viewfinders are overrated. The best EVFs are just as good.
Pros aren't married to glass or to viewfinders, though. They're married to lens mounts. Glass investment dwarfs camera body cost. That's the sticking point.
The worst part of the A72 was the battery and the buffer. The A73 made both of those concerns a non-issue.