I guess we just disagree.
Heh.
Of course it's yacht rock! It's got that quintessentially annoying smoothness, the "mature" lyrics< and would fit right in with pretty much anything by Michael McDonald. It's from 1977 - smack dab in the middle of the yacht rock/easy listening era.
Google "yacht rock" and "We Just Disagree", and there are plenty of cross-references. Most of the music press considers it pretty squarely in the yacht rock category. Here's a list of the "Top 50 Yacht rock songs", and We just disagree is at 40 or so.
https://ultimateclassicrock.com/best-yacht-rock-songs/
Down with yacht rock!