Given that DVD/CD drives are now more often external and connected via USB,
they do not conflict with your request for an alternative.
I agree that CD-R discs are not ideal, especially after having a couple go bad
on me after a few years. But you could instead upgrade to the compatible
M-DISC, where M stands for Millennium.
While I don't know if an M-Disc will really hold for a thousand years,
or that anyone will care about your data at that time, M-Discs have become
much cheaper in the last few years. For example on Amazon,
Millenniata 4.7GB M-Disc Write Once and Read Forever, Read 16x/Write 4x Speed, 50 Pack goes today for $124.95. You can also today find Blu-ray M-Discs.
You would have to choose carefully your DVD/CD drive for compatibility
with M-Discs. I have found this
M-Disc's list of devices that can write,
but I cannot vouch for its completeness.
If you wish to go up another notch, you could pass to WORM tape cartridges,
but there you are multiplying the price-tag by a factor of 10.
SD WORM cards seem to have gone out of fashion, while Flash-using WORM
seems not to exist. So as far as I can see, the options that are left are
CD-R, M-Disc or tape.