It's ok to be happy staying there as long as you are OK with being salary capped. The salary wasn't even my biggest issue. My biggest issue was my title and compensation didn't match what I was actually doing day in and day out which was everything.

If I decide to slow things down as I get older I may go back to just straight coding. I love it.

Senior dev is not what you were doing, judging by your description of it.

Specialization and experience is pretty much it.

It's quite depressing to watch others progress beyond the menial tasks whilst i seem to be in stasis.

i read for about an hour every morning. reddit, hacker news, newsletters. Gives you great exposure to everything that's out there and what's changing. I highly recommend just picking simple function you need to write and work on that in the mornings. work on building isolated, modular code. I tend to write more functional / interface bases code than OO these days. Easier to reason about and maintain.