Wired wrote an article in 2017 [1] on whether it's possible/probable to do that. Technology has evolved a lot since then, so it's a lot more feasible, but the article describes how far metadata alone can go.

For example, let's say an ad network knows your and your friends' location, and knows you've met because you've been close together frequently, or are using the same wifi network. You talk about perfumes, then later one of them looks up perfumes on their phone. Google would usually have access to this much metadata, and will likely serve you perfume ads because of your friend who later looked it up.

This doesn't directly answer your question though. The answer would be - it's possible, but a lot is possible without that.

[1] https://archive.is/OyuUO