> Good and accurate estimation is not just a dev function. It requires buy in and input from the entire business stack.

And in my experience, when people don't want to buy in to doing the whole process up front but they still demand some kind of commitment, the easy way to handle it is:

"We can commit to a date and we'll finish whatever we finish by then, or we can commit to a scope and it will take as long as it takes. But we won't commit to a date and a scope unless we spend the up front time to first figure out every detail of what we need to build."

Stating it like that usually makes people realize how ridiculous it is to commit to something, but you don't know what, but you'll still do it by a certain date. And it makes them feel like you're being willing to work with them/gives them some decision making power.