The more I think about the problem with wildshape, the more I think the real issue was with the 2014 Moon design.
Keep regular wildshaping as in 2014 (maybe restricted to PHB beasts). Then for Moon Druids, give them the modifications to their wildshape as they gain levels instead of the higher CRs. Additional damage, enlarge/reduce, AC bump, additional HP, multi-shape with one use (like the movie), resistances, etc. so that their wildshapes remain relevant for combat at higher levels.
That's plenty of utility for most Druids, and for those who want to fight as a beast, they have a good way to do so while still keeping the available CRs at 1 and under, so that designers don't have to balance higher CR beasts for Druids.