We aren't even responsible enough with the nuclear assets and waste we already have, and we're going to have to actively look after that lot for millennia to come. You can't just walk away from a spent fuel waste facility - you have to run it, or it will eventually leak radioactive isotopes into the environment. We aren't even doing that right now, so how do we expect our decendents to have the will and knowledge to do that in 2200? If we're still around at all.
We regularly build mines 4km deep with no water for several km around. Where are these radioactive isotopes supposed to leak to and why should we care?
If you have suddenly contact with rock from 4km depth there are not many scenarios where it would matter if it's radioactive.
That is simply untrue. The deepest operational facilities - e.g. Morsleben and Schact Asse II in Germany, WIPP in the US - are less than 1000m. There are a handful of others under construction, even more under consideration, but even if those all became operational today "regularly" at 4km would be a drastic overstatement.
Even with the facilities that exist, there have been incidents and concerns about groundwater contamination over the truly long term that many of these isotopes require. You present it as a solved problem but in fact it's anything but.
