I have to say I no longer review for MDPI, partially because so little of what they send my way has anything to do with what I know about, partially because I do find them a bit "icky". But I have done some reviews, and the papers might not have been amazing, but they were all people submitting real work, they clearly believed in. Review suggestions were made, and papers were improved before being published.

Depends on the editors, as with any journal.

Do they play a hard game with their oodles of special issues, sure. But it's also scientists that then contribute as editors or authors - not publishers making stuff up.

It's not because they provide easy bait that one should take it, hook line and sinker. For the community to then turn around and complain about predatory practices seems a bit hypocritical.

Some are predatory, some are iffy, some are mediocre, few are decent.