Even as a solo dev there's generally been a yawning gap between k8s and manual infra that nothing has ever filled that well and it's part of why things like Heroku were so popular for a while.

Well, maybe especially as a solo dev. Things like Heroku and other tools that were largely called PaaS at the time were very popular with individuals and small teams but they had limitations for enterprise development--and even ran into barriers once anyone ran into those limitations.