I can understand it's a stimulating problem for the brain.

In terms of priorities it doesn't make any sense at all to me though. It's hard to get the global population to care and act about what the GLOBAL state of the planet will be by the end of the century. So I really could not care less if by accident a few people dug a hole in tens of thousand of years at the wrong place and it created an issue. It's not like the whole human population would meet at this same spot and quickly dig a hole deep enough together so that they all get radiated...

It's not okay to poison people even if they are far away in space and/or time.

In my mind, continued storage of nuclear waste will always have to remain an active process. Dispose and forget like in a landfill isn’t an option if you care about the long-term risks.

That seems super unlikely to be a problem. For long term storage, I'd expect that we'll dig a deep shaft, or use an existing abandoned mine, and then seal it back up. Any group of humans who are willing and able to make a hole through several meters of concrete in order to get at the stuff will almost certainly also have the technological sophistication to know what radiation is, and that radioactive isotopes are dangerous.

Also, if you do decide to leave a message anyway, you'll just have to make it interpretable to a human, not to any possible "creature". 10 000 years is nothing on evolutionary time scales, so it will still just be us humans around, (or nobody at all, if we happen to go extinct first).

But in ten of thousands of years, all radioactive waste will be low activity, no? I mean, we do have prototype reactors that now use actanids as fuel, so the medium lasting high activity waste issue is now dealt with. Don't we only have to worry about the next 300 years for to radioactivity to go down to granitic cave levels?