Sure you can. I’ve literally had classes that worked exactly like that. I had classes where I had to interview and observe actual customers using our product.

What you’re describing is a huge part of engineering. Engineers have been doing this long before Product Managers existed. When I started, software engineers used to just talk directly to customers, domain experts, business analysts, and business leaders.

At “product led companies” the engineers just end up trying to figure out what the product manager actually wants because it’s not really possible in most cases to separate the what from the how.

Having worked with both systems, I don’t think the way it works now is better.