"Clean" and "affordable" map immediately and obviously onto wind and solar; what then happens is people engage in a lot of wrangling around "reliable" to push nuclear, requiring bending both "clean" and "affordable" quite a bit and running into an invisible other criteria of "quick to deploy" and "politically acceptable".
Speaking of countries, I could reduce this answer to one word, which refutes every single point you make: France.
And the EDF reactor project in the UK is of course overrunning on time and budget.
(when is the next French nuclear reactor new build scheduled to come on line?)
https://en.wikipedia.org/wiki/Flamanville_Nuclear_Power_Plan...
It's now behind. Basically no one wants to fund new nuclear plants. They're incredibly risky considering how front-loaded the cost is.
But the OP's question is loaded too. We don't need "reliable" right now. Fossil fuel can cover the reliability gap on the short term perfectly well. Until the question becomes "well, we replaced all the peak consumption with renewables, now what?", asking for reliability is status-quo propaganda.