I think this is a vital point. Estimates help narrow down what is important and what isn't.
Maybe you want features x, y and z. If it takes a day then X is worthwhile, if it's going to take a month don't bother. Z must be done so if that's going to take a long time we need to drop y.
One of the best product owners I've worked for would often ask for estimates and base plans and features from those. Some things would be easy technically and valuable, others harder and just a nice to have (but worth it if it only pushed things back a day).
I remember an interview at a well known tech-ish company where the question started out as “Estimate this project” with a good description of the scope and team. After I said something like 4 months, interviewer said, “OK. The CEO says it needs to be done in 2 weeks. What now?”
I thought this was a basic project management question about trading off quality, scope, schedule, staffing, etc. and offered the usual suggestions of cutting scope (nope CEO demands entire scope), cutting quality (nope can’t compromise quality), increasing the team, contracting out, reprioritizing and realeasing P1s in 2 weeks (nope, nope, nope). Obviously I didn’t get the job.
Later I learned from an acquaintance inside the company that the right answer was probably “Work the team 24 hour days, nights and weekends, for 2weeks to deliver what the CEO wants. I think I dodged a bullet there.
Maybe you want features x, y and z. If it takes a day then X is worthwhile, if it's going to take a month don't bother. Z must be done so if that's going to take a long time we need to drop y.
One of the best product owners I've worked for would often ask for estimates and base plans and features from those. Some things would be easy technically and valuable, others harder and just a nice to have (but worth it if it only pushed things back a day).