So although stablecoins exist which are great for predictable commerce (having a treasury of the amount value you expected), a key piece of the infrastructure is that Ethereum clients don't work over Tor.

Most stablecoin activity is on the Ethereum network, and the clients have never prioritized Tor use.

Ethereum also hosts privacy that all fungible assets can inherit, using Tornado.cash people can trade notes of unknown amounts, redeemable any time. Using Aztec people can make any token private, and communities can consider doing private-by-default tokens including with stablecoins if the issuer started it that way.

So its not as simple as Bitcoin OR Monero. There is a looming large piece of the puzzle that simply is missing one piece - ease of use over Tor. Layer2 solutions on Ethereum also inherit privacy inadvertently, while solving scaling issues on layer1.

Of course, sci-hub doesn't NEED Tor itself for donations, being fairly benign, but as soon as that piece exists, many tech savvy people simply use that route. Monero will likely remain superior but technically lesser solutions can solve the actual market needs better, since the attack surface isn't that consequential.