I don't work in this field, but I'd have a bunch of basic assumption you could dismantle:
1. We need a solid power grid, anyway, you know, for transporting electricity where it's needed. So shouldn't that stitching be quite solid anyway? Also, at a national level, I'd imagine solar and wind probably have rather solid statistical patterns, and those random factors can be abstracted away to a degree (the whole "what happens when the wind is not blowing?" - kind of hard to have the wind stop blowing all over 300k sqkm, all at once :-) ).
2. Once that power grid is solid, does it matter how small and distributed those solar and wind patches are?
3. I don't think Lithium-Ion is the only/main energy storage tech being investigated/invested in for grid purposes. And why couldn't it become a solid alternative for base load? Are base load-capacity energy storage facilities not competitive with gas/nuclear/coal power plants, factoring in pollution or other risks?