What tool should security professionals absolutely NOT be using?

It's difficult to say NO or something like that, it always depends on needs, accepted risks, and many other things...

Stop using the magic silver bullet!  There is no such thing as a magic silver bullet that protects against all security issues and concerns.

Stop wielding the “NO” hammer. Security exists to help businesses successfully operate even though there are risks. Saying no doesn’t help anything. Find a way to communicate and/or reduce the risk in an effective way so the business can continue to operate in an informed way.

If you're using Malwarebytes, dump Malwarebytes. Get rid of it. They are predatory. I had a population that was downloading the free version. Because they thought they were doing the right thing with the free version. Of course, they didn't understand the license that said, "Hey, the free version doesn't apply to the enterprise." Malwarebytes let that happen for three years and said, "Hey, you owe me." We owe you X dollars. And I was like, "You're kidding, right?" I will tell anybody and everybody forever, Malwarebytes used to be a good company, now they're atrocious. Stop doing business with them.