And to think they never have to worry about VACUUM. Ahh the peace.
Short version is that VACUUM is needed to clean up dead tuples and reclaim disk space. For most cases with smaller amounts of data, auto-vacuum works totally fine. But I've had issues with tables with 100m+ rows that are frequently updated where auto-vacuum falls behind and stops working completely. These necessitated a full data dump + restore (because we didn't want to double our storage capacity to do a full vacuum). We fixed this by sharding the table and tweaking auto-vacuum to run more frequently, but this isn't stuff you have to worry about in MySQL.
Honestly if you're a small shop without database/postgres experts and MySQL performance is adequate for you, I wouldn't switch. Newer versions of MySQL have fixed the egregious issues, like silent data truncation on INSERT by default, and it's easier to maintain, in my experience.
“Stops working completely” should not be a thing, it could be vacuuming slower than the update frequency (although that’d be surprising) but I don’t know of any reason it’d just stop?
That being said I’ve also had issues with autovac (on aurora to be fair, couldn’t say if it was aurora-specific) like it running constantly without vacuuming anything, like there was an old transaction idling (there wasn’t)
In any case, this got resolved but caused a huge operational headache, and isn't something that would have been a problem with MySQL. I feel like that's the main reason VACUUM gets hated on; all of the problems with it are solvable, but you only find those problems by running into them, and when you run into them on your production database it ends up somewhere between "pain in the ass" and "total nightmare" to resolve.