Yes, what you are missing is reality.

You can either build renewables to replace fossil fuels in the next years (and if the build-up doesn't work as fast as you want to then it will takes a a few years more to reach zero), getting less and less every day. Or you can build new nuclear reactors and just keep burning coal full steam for 5 years, 10, 15, probably 20. And then you reactors are finally online, but electricity demand has increased by +100% (and further increasing...) so you burn more coal for another 5, 10, 15, or 20 years...

The exact same thing happens btw right now in basically every single European country that promotes nuclear. Because nobody is building enough capacities to actually cover the minimal required base load in 2-3 decades (electricity demand until 2050 will raise by a factor of 2,5 at least - because most countries today only cover 20-25% of their primary energy demand with electricity but will need to raise that to close to 100% to decarbonize other sectors; so we are talking about about a factor of 4-5, minus savings because electricity can be more efficient). They just build some and pretend to do something construtive, while in reality this is for show and they have basically given up on finding a solution that isn't let's hope the bigger countries in Europe save us.

For reference: France -so the country with optimal conditions given their laws and regulations favoring nuclear power and having a domestic production of nuclear reactors- announced 6 new reactors with an option for up to 8 additional ones and that they would also build up some renewables as a short-term solution to bridge the time until those reactors are ready. That's a lie. They need the full set of 14 just for covering their base load for their projected electricity demand in 2050 and that's just ~35% of ther production with the remaining 65% being massive amounts of renewables (see RTE -France' grid provider- study in 2021). Is this doable? Sure. It will be hard work and cost a lot of money but might be viable... But already today the country with good pre-conditions and in-house production of nuclear reactors and with a population highly supportive of nuclear can't tell it's own people the truth about the actually needed investments into nuclear (and renewables!), because it's just that expensive. (Another fun fact: The only reason why their models of nuclear power vs. full renewables are economically viable is because they also planned to integrate huge amounts of hydrogen production for industry, time-independent export (all other countries will have lower production and higher demand at the same time by then) and as storage. So the exact same thing the usual nuclear cult here categorically declares as unviable when it's about renewables.)