If you are concerned about carbon in the environment and do not support fission for electrical generation, You Are Not Really Concerned About Carbon.
No, that is complete bollocks.
No. Actually it's not.
If you purport to be concerned about carbon in the environment, and you don't support modern fission for electrical generation?
You, quite simply, have NOT thought through the equation well enough.
While some of the renewables COULD be built to a point that you could use them, in conjunction, for base load, the main problem is that the power STORAGE technology for such an undertaking just doesn't exist.
Without that, the build-out for a complete system is several orders of magnitude LARGER and several more orders of magnitude more intricate. This makes them totally unfeasible from pretty much EVERY logistical standpoint.
Yes, granted, we COULD build enough nuclear capacity to cover energy consumption for the entire planet for years/decades/centuries to come (both base and peak).
That's uneconomical. We're better off building nuclear to cover base load in the truly foreseeable future (basically over the 50 year lifespan of a typical generator), and then augmenting with renewables for peaks.
Once that's done, LOTS of research (and MONEY) needs to be poured into two things.
1: Fusion
2: Improvement of storage technologies/methods.