No affiliate links means they're paid to review. Affiliate links means they get paid for people visiting.
Basically someone gotta get paid to put in the work. It is increasingly bad as a practice to review things negatively. So generally incentives work towards good reviews.
One sign though that a review is very biased... If they give you a discount code. They are not reviewers, they are salesmen.
I don't think this is a good rule of thumb. There are lots of people reviewing things without getting paid to review.
And affiliate links are a variation of getting paid to review. They make money if you buy what they're reviewing, after all, so are incentivized to encourage you to buy.
ultimately. people need to get paid.
i view groups who tend to have great respect in the community and generally own up to their mistakes as worthy voices. when you don't know someone and need to judge who they are, i find that admission of mistakes to be the biggest indicator of trust, vs those who effectively downplay or claim they don't make them.