I would love to say we can build renewables and nuclear. But let's look at the actual reality: Not only are most countries with a nuclear plan lacking proper amounts of renewables (because for more than a decade an anti-renewable streak was part of nuclear lobbyism - see the amount of people here or anywhere else hallucinating about "expensive renewables" when their own model of electrity generation needs those renewables (and even some storage) to be viable), it's even worse. Most of these countries aren't even able to build nuclear on the proper scale they would need.

So no, there is no technical reason we can't build both.

But real-world experience right now shows us that most can't even get the proper build-up of nuclear alone done. Explaining to their heavily desinformed voters why they need to build massive capacities and also need to build even bigger amounts of renewables seems to be indeed impossible right now.

The other thing is time frame. If the already agreed upon climate goals give you a remaining co2 budget for another 6 or so years, you can indeed not start building nuclear now. That would have been a wonderful idea a decade or even longer ago.

There is actually only one undisputable thing we need to do right now: build up renewables and massively so. To stretch out the remaining budget (via constantly reducing CO2 emission quickly) to 1-2 decades and use that time to a) either build up storage and infrastructure or nuclear base load. The difference is that the infrastructure and storage can be build in steps alongside renewables while the nuclear base load would need to start today. And most countries seem unable to do it, with the deciding factor being costs. Costs they would also mostly need to pay now in advance.