Figure 1: From NREL Renewable Electricity Futures Study
Very few people out there are arguing for a 100% nuclear future, and most are not arguing for a 100% renewable future. When we toss the extreme views out, the debate is over how much of what.
If you bound your debate to electricity generation in 2017 in a given geographical area, say, Seattle, you get:
Natural Gas 1.3%
Not bad. Who said you can't cost effectively decarbonize with renewables (when 87% comes from hydro)? Doing that with wind and solar, on the other hand, remains an untested hypothesis.
If you bound your debate to electricity generation in 2050 in the continental United States you might get what you see in the lower half of Figure 1 above, which encapsulates the four-volume mega-study from the National Renewable Energy Lab to replace 80% of our electricity generation with "renewable" sources.
If you can't trust the NREL to come up with a competent study biased to favor renewable energy, who can you trust?
Some things to note about that study: