But in the context of ransomware, the advice presented here is game-theoretically sound (and proven by thousands of years of experience in dealing with criminals demanding ransom), so I do trust it.
Not the big ones that are well-known names in the PC market. There are quite some shady security software vendors out there, and a handful very competent ones that I trust if I have to.
The bad ones are typically well-known desktop anti virus scanners that try to score by showing you a high number of threats they allegedly defeated. If you look at those threats in detail, they turn out to be browser cookies, or bookmarks, or something similarly trivial.
A good (but not exhaustive) test is to look at what the vendors promise. If they promise you full protection of your machine or network, you know they are full of shit. If they talk only about one aspect (identifying attackers, reducing the attack surface on a browser), things start to look better.
I don't trust them to make good quality software which works quietly and efficiently in my interest.
They basically sell a security theatre product where their motivations are to popup "PROTECTED BY ____" at all times so I don't forget it exists, and to look busy - typically by scanning the same files over and over even though they haven't changed in months - and to hook into everything to add more sales buzzwords to their product.
Do you trust makers of security software?