Yes, something is lost, and that something deserves to be mourned. It's a big change and it will take some time to figure out what math looks like going forward, so if you are upset that is totally valid. But... this has potential to be amazing. If we can prove anything with the snap of our fingers, let's see how far that can take us. Let's explore unknown areas of math. Let's develop new fields to unlock new understanding.
Secondly, what Grant didn't touch on was a different fear I have. The fear of what will happen if all this power is centralized into a few companies. It's hard for me to envision a world like that and be very excited about it. Math has almost always been accessible to nearly the whole world. If that changes, I don't see that being a good thing for any of us.
That's why I feel very strongly that open models and open source are the best path forward.