I started ignoring MDPI emails entirely. I even know someone who is threatening legal action against them because they refuse to stop asking him to review paper

I started ignoring MDPI emails entirely. I even know someone who is threatening legal action against them because they refuse to stop asking him to review papers for them. The problem is that it poisons everything. It's not just those bribing, it makes everyone suspicious of legitimate journals too. Scientific literature in general is devalued by these paper mills. Now every scientist has to keep a list in their mind of "reputable journals". And guess what, those journals aren't that great either!