I do use the Amazon ratings.

I look at the one star ones. If their complaints look reasonable and consistent then I know it is crap.

The only reviews to trust are from consumer reports and which? Who buy things retail and not free from the manufactures and they have been doing this for 60 years. Even then Read the reviews carefully and the user comments.

People use bot farms to kneecap their competitors with fake 1-star reviews, so you can’t trust them either.

Yes but you can usually tell if a complaint is reasonable - and I see many less one star than 5 star reviews

Feels very dangerous to install extensions that have full access to the contents of every site visited..

That’s a good point. I’m extraordinarily lazy about security. Maybe you could make one browser profile to look up products, and your usual one to buy them.