Hey Travis – Zone 1 does help improve aerobic capacity, endurance and helps facilitate mitochondria production. Alan Couzens has studied and written a lot on this topic. He is a well-regarded endurance coach that has coached many athletes to great performance victories. During his several decades of studying and coaching, he found that spending significant time in Zone 1 is very beneficial to an athlete’s development.
You can find his substack and book at the link below. I am a big fan of spending time in Zone 1 & Zone 2. Consistency with training and increased volume over meaningful periods of time will help build a great aerobic base.