I typically wouldn’t want to use Tor for anything more than textual content as it puts too much load on the Tor network.
While I agree that the Tor network is slow, it also depends on excess traffic to “bury” the more sensitive stuff. Part of why Tor works is because the actual sensitive stuff gets buried under all of the noise of regular users. Without all of that excess traffic, it’d be much easier to track what is happening.
As an extreme example, imagine how insecure the Tor network would be if there were only two users. It’d be blatantly obvious that those two users are communicating. By adding more users and more traffic, those two users can more easily hide in the sea of traffic. In short, more use does slow things down, but it’s also better for privacy overall.