I think that the cost of maintaining a site over 200,000 years is a fair point. That said...is it better or worse than coal? Because practically speaking, that's what the choice is here, as far as I can tell. I'd love to say we can quickly convert the whole world to pure renewables, but it's very likely that we can cut our GHG emissions fastest using a mix of multiple approaches rather than ruling out the good in favor of the best.
And note that when you consider costs of something that you have to make a payment on in perpetuity, we don't calculate that as an infinite cost[1]. To say that we'll have to safeguard this nuclear waste in, say year 100,000 of its lifetime, is a lot less of an ask, simply because we have no idea how advanced human technology will be then, maybe making the problem trivial, or whether humans will be completely gone, etc. I agree it's important to think about future generations and to have a very long term view, but the problem of nuclear waste seems much less urgent than the rapidly mounting costs of climate change. Even if we end up using nuclear for, say, 100 years while we transition to completely sustainable, renewable energy, that would be a win over continuing to use fossil fuels. And I don't think it would even add that much to the existing burden of dealing with nuclear waste. Maybe in 200 years we find a spot and put all the waste there with big warning signs etched in stone, and then the main cost is only one of ensuring that we main translations and records of the danger of the site as language evolves. Dealing with solid waste, however careful you need to be with it, seems much easier than trying to collect gases that have mixed into the atmosphere.
[1] https://corporatefinanceinstitute.com/resources/knowledge/fi...