They’re similar, but different.
Interesting insights are the one that makes people goes, "Wow, that's new." But people can't do anything about it. It's interesting but irrelevant.
Useful insights, on the other hand, provide good patterns and signals to make a decision. A product manager can see the insight and go, "Okay, with that in mind, I think it's better if we do X."
To find useful insights, make sure to be clear on what decision you want to make. If you understand the decision point, you can plan better. You can ask better questions. Ultimately, you can synthesize the data to be relevant.