I tried many things like unblocking URLs in the firewall (https://translate.kagi.com), whitelisting, etc. Performance is poor, irrespective of the browser.
For https://translate.kagi.com/proofread to take 1.37 minutes in Best mode to proofread less than 100 characters, I'd say it's unusable.
Looking at the browser console's network tab, it seems that several scripts, CSS files, and some SVGs are loading over HTTP instead of HTTPS, which, in my guess—I'm no expert—might be responsible, but I don't know.
Some examples show up in the "initiator", such as "xhr" and "NS_BINDING_ABORTED", in network monitoring. Please look at the attached screenshots taken from the browser's console to see details.
To be of practical use to proofread text and apply corrections.
