Discussion here: https://community.metabrainz.org/t/batch-voting-check-boxes-disappeared/403979

Behaviour appears to have changed some time around the 1st November server update. Some people have said "Why not use @jesus2099’s mb.POWER-VOTE script?", which may be a fair comment, but as I don't see anything in the list of 1st November changes stating that this useful feature was intentionally removed, I'm guessing its removal was unintentional.

I'm voting a lot less as a result, and others probably are too.