I don't think a lot of people on this forum use trustpilot a lot, but I am pretty sure that a lot of people are still using it. A lof of the reviews on there are from people that have a bad experience (mainly due to their own fault as they probably broke some rules) or are just fake reviews. Once a while, you find a legit review, but I always browse around if I want to read some reviews.
I still think that only the people who want to leave a bad review are using it, that's about it. I do not think that people go "let me check their rating on trustpilot" to see if a casino is good or not, I mean even some of the biggest names in all of casino world do not have good ratings there, people would end up playing at some of the worst places ever if they really want a high rating, because there aren't that many customers for those small terrible places, so only a few good reviews are there.
If you look at any with thousands of reviews then you will realize that at the top of rankings, there aren't that many great ones. This is known, if you are already aware of this, why would you want to look at the rates there? You wouldn't.