It puts me in mind of making a jig when woodworking. Make the thing when you need it. You don't need to maintain it, you don't need to sell it. It does it's job and you move on. If it does the job really well maybe you keep it around for next time, maybe you refine it if you use it often.

Never be ashamed of making useless things, the really useful things are hiding amongst them.

If having fun is interfering with your productivity, that isn't necessarily a problem, it is only a problem if it interferes with your livelihood.

If Robots are to take all our jobs, we need to retain our livelihoods. Then we all could perhaps have fun making the things we want to make for the pleasure of making them.

I too have ADHD, perhaps it is different for me because I began medication about the same time the models got good, but I have worked on some individual projects for longer than I could have earlier.

I don't spend all day typing prompts though. It's more of a step in, do a thing, then think about it while doing something else.