Please help me understand why arguments for the viability of renewable energies can rely so heavily on "its possible to make the tech better, the tech gets better over time" but this phenomenon is never afforded to something like fission.

For the record I support both. It's just so bizarre to me to see people list out numerous problems with fission and say see that? See all the problems this tech has?

Theb when all the challenges associated with renewable energy are raised, the resounding response is "the tech will get better, just give it more time"