I have some rare media that I know would be extremely difficult to replace, so I back that up, but the general stuff is less important.
However, with rights holders constantly trying to move away from the idea of permanent physical ownership, some media will become harder and harder to find in their best or purest forms, disks will go out of print and the used market will start to slowly die as media ages and rots.
you can pirate on a kindle it’s just more annoying to do
Kobo is the go-to for bang for buck readers that don’t care where your files are from and have good format support. got my dad a libra 2 and it’s great, especially with the physical page turn buttons. the default reader opens most files just fine, but you can also put KoReader on them for more functionality without too much hassle.
Personally I use an older Boox Note 3 which is easier since it runs android, but is massive overkill to be used as just a reader, i use it as my main tablet and a notepad/sketchpad.