> I feel like a freaking loser given my age and my relative career stagnation / my inability to actually turn my mildly above average skills into any real money.

There's a lot of noise out there that tells us we're supposed to get rich off of entrepreneurship or VC money, and not enough telling of the truth that those success stories are pretty rare. No one who is doing something they at least minimally enjoy and not breaking their body doing it, and getting paid in the top 20% of income earners, is a loser.