I did a poll and nearly 30% of the people who voted said they used Sync! It's stayed around that percent the whole time too!
EDIT: Here is the poll I forgot to put this here like five times lol https://strawpoll.com/wby5A21R1yA
That's probably why people are mad. I've seen lots of comments to the effect of they don't want Redditors here because they'll "ruin" Lemmy.
Sync makes it harder for them to gatekeep.