The discussion is about if humans had influence on climate, not about climate change itself. Although you could argue how much a of an discussion 97 - 3% is.

Regardless of cause:
- You still have to prepare for climate change. That’s not up for debate. So more water management/defences for the higher water levels, more preparation for extreme weather, etc.
- Fossil fuels is still going to run out eventually. So you still have to look for an alternative eventually. And it causes enough other pollution during production and burning. Even if it does not affect climate change, you can’t deny smog, higher respiratory problem with people living near mayor roads, etc. Not to mention the political problems with fossil fuels.

Beside I personally like to keep non-renewable resources in enough supply so we can use them if we figure something especially useful with it.

For example helium is non-renewable resource and with current use in not exactly important things like party balloons, it might not be available in 25-30 years’ time to cool MRI scanner, radiation meters, etc. Who knows what people can figure out with fossil fuels other than just burning them in the future.