Freenet in fact is less vulnerable to that because they aim to prevent that specific attack you described with the following feature:

It offers a "darknet" mode where you manually add peers by exchanging cryptographic keys with them.

The connections to those peers are fully encrypted then and thus very difficult to block because you can't detect Freenet with merely packet inspection anymore.

Besides, the ability to censor individual Tor sites is *bad enough* already IMHO.