> Wh/kg figures hasn't changed

Maybe I misunderstand you, but taken at face value, this assertion is incorrect.

Battery density (Wh/kg) has more than quadrupled since the 90s. See e.g. https://rmi.org/the-rise-of-batteries-in-six-charts-and-not-...

Price is also dropping fast!

The learning rate for Li-ion batteries right now, is around a 35% price reduction for every doubling in installed capacity.