Maybe it's counterintuitive, but I think the "jack of all trades" role should be given to someone who's very senior, but isn't focused on career advancement.
It sounds like you got stuck learning more trivial things before you had a good foundation in something more substantial (like C or UNIX).
If it weren't for the rampant ageism in the industry, that job might be a perfect fit for someone in their 60s who has already written a few million lines of C and is happy to help less experienced people just get unblocked.
Instead it often falls to the "junior senior" because the "senior seniors" are all pushing 30 and need to work on portable skills.
(Just my observation of the industry, maybe your own case was different.)
It sounds like you got stuck learning more trivial things before you had a good foundation in something more substantial (like C or UNIX).
If it weren't for the rampant ageism in the industry, that job might be a perfect fit for someone in their 60s who has already written a few million lines of C and is happy to help less experienced people just get unblocked.
Instead it often falls to the "junior senior" because the "senior seniors" are all pushing 30 and need to work on portable skills.
(Just my observation of the industry, maybe your own case was different.)