The concern that some future civilization will manage to dig so deep, in an area with no natural resources, crack open some of the waste caskets, and then die because they fail to figure out it is poisonous is one of the most ridiculously far fetched concerns. Contrast that extremely remote possibility with the certainty of pumping toxic greenhouse gases directly into our atmosphere. I cannot fathom why one would believe the former is preferable to the latter, but some countries like Germany seem to have made that conclusion.
And this is why nuclear waste disposal is _not_ an overblown challenge. Because even though there are already digs in place, almost all of the waste still sits right by in-use reactors. The US has been trying to fix this since the 80s, and afaik real progress has not been made since the bill to put it in Yucca mountain was killed in 2010. It might be a political challenge rather than a technical challenge, but it is an _extremely_ difficult political challenge that should be deeply considered when supporting nuclear energy. It is not really safe or cheap for it to stay above ground by reactors forever.
We're already fucking over future generations with a massive carbon footprint. Replacing all that with nuclear would be objectively less bad.