I use an old iPod I refurbed myself with microSD storage instead of a hard drive, a big battery so it lasts a week between charging and Rockbox so I don’t need iTunes.
It’s small and the physical controls are easy to operate while its in a pocket.
The audio quality is fine since I mostly use it outside the house when the music is competing with ambient noise like traffic, other people’s conversations, the noise of being on a bus or a train, etc… These aren’t quality listening environments.
My iPod was a fun pandemic project. If you want something portable, there are plenty of new devices you can get with more features for less money.
“Investment”? No. Consumer products should not be considered investments.