Fusion has great potential, but is probably being held back by a lack of community support, the slightly-higher-barrier-of-entry of node-based workflows, and the subtle but annoying ways in which the software can work against you.

TLDR: it does some stuff slower than ae, but nodes allows it to very easily do a lot of stuff that ae struggles with.

It's also a lot easier to parse since node->properties is less nested than comp->layers->effects->properties (and this makes a big difference on cognitive load).