They deal with exactly the problems you're imagining. How do you convey danger to a civilization 100,000 years in the future? How do you get them to take your warnings seriously? (We'd ignore any warning in the Egyptian pyramids created only ~5,000 years ago) How do you handle earthquakes and other natural disasters?
I found it interesting and you might too.
However, if we do assume civilization collapses and people forget about what radiation is, we can also safely assume that the future civilization will not be industrialized. If the waste is stored in some place extremely remote, inhospitable, or miles underground, the sheer cost of trying to reach the material would bankrupt any future civilization. We do have some precedence for this, one of the Great Pyramids was meant to be dismantled but it just proved too expensive: https://en.wikipedia.org/wiki/Pyramid_of_Menkaure
The problem is to communicate "radiation danger" to someone 10,000 years from now who doesn't use our language, alphabet, or iconography. That's not easy. Not impossible, but not easy.
The other problem is devising warning signs that will survive 100,000 years...
Hopefully the skin of the first group of people to dig up our waste sliding right off their bodies will send a strong message.
At 100k years, there could be generations between such attempts, and accounts could likely themselves take on the form of incredible (in the literal sense of "non-credible") legends.
Effects from lower-level contamination might be less pronounced, e.g.:
Worse, the 'mummys curse' became a part of popular culture!
In the same way that the dangers of radiation were found fairly quickly from usage of radium in paints, anyone in the future will probably figure out pretty quickly something is wrong.