I haven't started speedrunning yet, so I could be chatting shit, but the things you value about speedrunning seem very familiar to me.
I'm working towards a career as a professional drummer, and the practice one has to do sounds very similar to what you describe. My practice routine often is simply taking a particular drum pattern and playing it at one tempo marking twenty times in a row with no mistakes. If I can't do it at 100bpm, I move it down four clicks to 96 bpm, if I still can't do it, I move it down to 92 bpm and so on until I can do it twenty times in a row. Then I go up 4 clicks, if I get the next one wrong, I go back down four again, and so on.
So if I have a difficult song at 170 bpm, I have to break it down into individual sections and do this with each section until I can work my way all the way up to 170bpm, I then have to start putting the sections together, which often means going back down to lower tempos before going back up again, but the process is the same.
This is a really nice 30 second video to demonstrate the basic concept.
The process can really be a grind, but it's SO worth it when you start to reap the rewards.
Alec makes some excellent points in his post, though I disagree that what comes to fruition is worthless unless it can be measured materially; I think the feeling of doing something sick and also bringing joy to others who appreciate your work is a noble end in itself. If I play a gig where I nail a super hard song that I totally sucked at a few months ago, and the crowd love it, but I don't get paid much, I don't view that as "worthless". I gave a bunch of people a great experience watching me demonstrate my skill, and that makes it totally worth it for me. My ultimate goal would be to be able to quit my job and play full time, but tbh I see that as a potential bonus of the primary goal of just doing something I love really well.
I find that having a skill helps in other areas of life too, I used to be super awkward around girls, but getting really good musically helped with that too, as it meant I had other shit going on in my life other than just feeling angsty and horny. Got rejected by a hot girl? Well, that sucks, but I can still go home and practise soloing over the top of latin foot patterns, which is
AWESOME. Consequently, I started being far more carefree in social situations, and just gained more confidence in general knowing I rock at something.
What are your interests? Maybe that would help give a clearer picture regarding things you could immerse yourself in?