I think there are also 2 senses in which it's difficult to determine quality. The first sense is just that many things require expert attention, special tools, and or a lot of time to evaluate the quality. And for niche items, there might just not be a reputable reviewer out there. This is frustrating, but somewhat unavoidable.

The second sense is more insidious. Sometimes companies deliberately obfuscate the source and identity of products, making it difficult to even know if a product you saw a review of is the same product you'll get if you buy it now. I believe companies also do this simply to make price comparison impossible.

This is an abominable practice, and in my view should be extremely illegal. I'm very much a free market guy, but clearly labeling and identifying the products you sell should be a bare minimum requirement to gain access to any market.