So the choice is either anonymity and crime, or no anonymity at all. And crime won't go away, it just won't be able to use an anonymous channel for communications.
And it's not like criminals are getting away with it by being anonymous either. If you go on tor to commit crimes then you will be hunted down by the international police. And if you commit heinous crimes against children then you will find no refuge. That's not a good life to live. Odds are you will end up in prison sooner or later.
As in, 28.8K or 56K or so ...
This would force tor into being a text only communications channel which would obviate many of the most egregious illegal use-cases.
You'd lose nothing with regard to freedom of speech and thought and communication. For instance, you can publish, and consume, a site like HN without any issues on 56K.
But I don't see it working in reality because there is the argument that you might need to share leaks anonymously and that would take days.