And let's be honest, it's not like there hasn't been spent a decade or more, with thousands of developers working tirelessly on making Android as good as it is today. Like linux laptops not burning up immediately is itself a change upstreamed from android development, but that's just half of the story.

A mobile OS fundamentally needs a different application model -- apps can't just decide to run whenever they like. How will desktop GIMP know that it shouldn't waste my battery when in the background (unless it very specially requests it throuhg an API made just for that)? Does suspending it work as you expect? For how long will you suspend it, shouldn't you kill it as well after a while? Who saves stuff?

I can't help but feel that anyone strongly advocating for a GNU Linux phone (because let's be honest, Android is the linux phone) is just not familiar with the actual context of what it entails.

No one is running gimp on their phone, besides for laughs. There are a number mobile-centric apps in the repos, stick to them and you'll be fine.