And arguably it's worked pretty well for that, given that there's been consistently lots of horrible content for 18 years. Content providers (and users) have been busted, but that hasn't eliminated much of their content.
However, being a pure P2P system, you only have "anonymity" through plausible deniability. And that's a dangerous game to play. Criminal investigators have used modified Freenet nodes to track chunks of illegal content, and have prosecuted users whose nodes processed those chunks.
The Freenet Project argues that it's impossible to reliably determine whether nodes are requesting those chunks, or merely relaying requests from other nodes. But if you end up in court, you'll need an expert witness to convince the jury of that. So you'll likely end up with a plea bargain.
So anyway, it's safest to run Freenet on anonymously leased VPS, and access its webGUI as a Tor .onion service. Just as you'd prudently run a BitTorrent seedbox.
There’s no way to make the change you’re proposing without seriously compromising the set up of such digital, secure communications, though. You’re asking to MITM the secure net, as a feature.
You and the feds, both.
I guess you would need to use cash, at a minimum.
Then lease your VPS. And if it really matters, you can daisy chain VPS via Tor .onion SSH.
Simply exchange them to Monero. If you want, mix them, but only a single pass is needed. A mixer is a trusted 3rd-party, which introduces serious counterparty risk, and vulnerable to multiple forms to input-output correlation attacks, in the worst case, provides no security.
If you are paranoid, create multiple Monero wallets, and send the funds back and forth, each time with a randint(1, 100) hours delay to frustrate timing analysis. Please note that you should only run full node Monero, and must run it inside Whonix, otherwise, the unencrypted Monero traffic is exposed. The situation of P2P-level encryption of the entire cryptocurrency world is a disaster, almost all traffic is clear.
Ring-CT is possibly not the best cryptographic implementation of transaction anonymity, but currently the best practical implementation available. CoinJoin is a P2P version of mixer, but has no wide deployment, zn-SNARKs involves cutting-edge cryptography and provides 80-bit security (read, not confident), but 90% of Zcash transactions are clear transactions, makes private transactions vulnerable.
Or, once GNU/Taler is available, making an anonymous payment would be as easy as using PayPal.
... With a credit card (which of course has your name on it), since AFAIK the providers tend to only accept bitcoin for established accounts.
Cockbox (Bitcoin and Monero) at https://cockbox.org/
HostSailor (cards, transfers, Bitcoin, etc) at https://hostsailor.com/
Trilight Zone (cards, transfers, Bitcoin, etc) at https://www.trilightzone.org/
VPS.BG (PayPal, Bitcoin, etc) at https://www.vps.bg/en