Yes and no. There's no doubt they often act like echo-chambers. However, there are also innocent examples of them enabling discovery, e.g being recommended a kn

Yes and no. There's no doubt they often act like echo-chambers. However, there are also innocent examples of them enabling discovery, e.g being recommended a knife skills video after watching many cooking videos - it's in the general domain you're interested in, but was probably something you hadn't considered before.