One of the joys of the iPod was that I didn't really have to worry about charging it on a regular schedule. It would hold its charge for a long time. Eg, I took it bike camping and listened to Hardcore History's multi-part episode on Genghis Khan over a couple of days, with no need to charge up.
That's no longer the case. The battery life has gotten worse over the last couple of years, likely from age. It now doesn't hold a charge for more than a couple of days. I suspect that if I buy another old iPod then its battery will also be 10 years old and not in good shape.
If I don't find a good option for new hardware, then used is definitely a backup alternative!