Many regard MDPI as a predatory publisher. That's not a universal view and there is clearly a substantial amount of valid research that appears in MDPI journals

Many regard MDPI as a predatory publisher. That's not a universal view and there is clearly a substantial amount of valid research that appears in MDPI journals. But they seem to have a bias towards accepting papers with cursory review and collection of article processing fees. For example, they ask that peer-reviewers submit reviews in 7 days or less, which is something few experts are going to have time for. Then there is the matter of MDPI creating deceptive journal titles like _Cells_ which surely is often confused with the incredibly prestigious journal _Cell_. Anyway, caveat lector.