Have you tried going back to the theory of Flow, and the conditions for it to happen, and compare&contrast your current situation with earlier ones?

I suppose that the differences might be subtle. For one example, for the condition that you have a sense of doing a good job, your metric for good job might have changed: it might no longer be simply make an algorithm to do X, but include larger context, including the reason X is being done.

BTW, keeping in mind that techbro ageism is a thing, especially in YC-type circles (that's how YC started), I suppose that HN comments by over-30 people can be fodder for confirmation bias by 20yos.