I only wish I could find these "a little bit empty", "80-85%" flights. Any flight I've been on in the past 4 years has been filled to the brim and gate-checking

I only wish I could find these "a little bit empty", "80-85%" flights. Any flight I've been on in the past 4 years has been filled to the brim and gate-checking anyone who didn't pony up for Premium Economy or better - or even outright oversold and handing out "please take the next flight?" vouchers. (Seattle is my home airport, so maybe this has something to do with it - but come on, SEA is no ORD or ATL...)