I picked up a bass guitar for the first time ever on my 49th birthday, so I'm struggling to see your age as being somehow 'over the hill'. 😂
Now is a LOUSY time to be selling valuable kit. The market is in the toilet and will likely stay there for the whole of 2023, so don't sell nuthin' unless you're desperate.
If you're working hours that make it hard for you to join a band, why not invest some time into starting your own band, built around the hours you CAN play. You're not unique ... there will be other musos in the same position as you; hopefully one will be a drummer, and another will be a guitarist. You never know until you try.
And @Steve Browning is absolutely right. If you want to improve generally as a musician, learning to play keyboards has to be the best bet. It's also age-proof. Nobody ever pointed at a seated keyboard player and said, "Well that's not very rock'n'roll, is it?".