Most things have already been said, but here my personal list:

• No way to get properly rid of waste jet
• Quite unreliable (AFAIK one of the French ones only operated half the time it should in 2024)
• Recourses for it are generally supplied by oppositional nations
• If they blow up it’s bad, even if they don’t by themselves they might through third party influence
• Generally positioned by politicians as an excuse to not build renewables, not replace fossil fuels
• They are a entry point for building nukes, their existence making anti nuke treaties hard to control

Most importantly: they don’t make financial sense. Renewables provide the cheapest energy and even the required energy storages can compete on the market. The French Court of Auditors published a statement after one of the more recent power plants were openened that basically just: stop building fucking nuclear power plants they cost way to much