There are solutions, but they come at a steep cost with regards to usability, so would shrink the anonymity set to what would be an unacceptable level for the u

There are solutions, but they come at a steep cost with regards to usability, so would shrink the anonymity set to what would be an unacceptable level for the uses Tor cares about. The reality is that these attacks, while theoretically possible, require more work and money than the rewards justify (you can't just bulk buy nodes from a provider, Tor doesn't allow connections that route to the same host or close IPs, and does somewhat regularly block relays that were all created suspiciously close chronologically without identifying as the same operator), so are considered an acceptable risk. Snowden was willing to rely on Tor, the rest of us who just want some extra privacy will be just fine.