We haven't solved the "disposal" question of using fossil fuels, and those turned out (or were known along) to cause much bigger problems.

Like most things with environmental impact, we just let later generations deal with it. Somehow.

Mostly, yes. Use breeder reactors to turn long term radioactive waste to sort term radioactive waste, store for short time and done. The downside: it's more expensive to move and process the stuff so nobody wants to do that.

Next question would be:

Who pays for disposal and dismantling old nuclear power plants? Might also be relevant for @Eximius@lemmy.world claim. I guess it‘ll be the tax payer. And then we might have a different answer to the question of financial sense.

Privatizing gains and collectivizing costs still seems to be en vogue.

Relatively yes. There are disposal sites under construction that are in highly stable and environmentally safe locations. One good thing right now is that radioactive waste is temporarily easily stored. Transport of waste is an issue still, but far less of a problem than transporting oil and oil products.

We have, but of course not to the satisfaction of anti-nuclear activists because solving it would be counter to their actual goals.

Nuclear waste is actually quite easy to deal with unless your purposes are best served by it being very difficult to deal with, in which case you make as much trouble as you can for it.

Uh... Yeah. The reactor was in operation until 2019 when it stopped being profitable. Disposal was never a problem.