I don’t think nuclear waste is a huge deal, but it does increase fuel costs in a very meaningful way. The classic uranium is cheap therefore nuclear’s fuel is cheap is a tiny fraction of the story. Refueling generally means weeks of downtime, you can’t safely operate at extreme temperatures for maximum efficiency, you need enrichment, and fuel rods, and even with multiple trips through the reactor core a significant amount of fuel isn’t burned or economically useful, and when your done you also need processes do deal with highly radioactive material + the costs of dry casks, and then transport them offsite and then down into some tunnels.

Add all that stuff up and fuel is a major expense. Granted that downtime depends on the design, and is also used to do other maintenance tasks but without refueling you’d end up with different tradeoffs.