I liked how the DOTM and Prime series handled Cyberverse by taking advantage of the reduced size to be able to make playsets and vehicles that would never fly at the standard Deluxe and up scale. It really set the scale apart from Legends, which until then was just low-budget versions of better toys.
This, for me.
Core was cool on a few levels; one, it allowed for this, where we'd get little versions that could hang with the Titans (it seemed tailor made for Kingdom, where there was an Ark they could be displayed with). Two, it offered a venue for characters who had to be that size in the rough scale that they do.
The problem was multifold, and tied to each of those. First, you need a big line and not one price point to cover a satisfying amount of cast members. As it was, we got a handful of molds and their redecos. Then branched out of G1, giving us random one-offs that had no one from their casts to hang out with. Original Cyberverse committed, and more or less completed admittedly smaller and tighter casts. (To be fair, most of those were Legion class, so not really analogous to Core class?)
Second, they keep redoing the small characters and scaling up anyway, just like they do with everyone else, so the other source for the line gets cannibalized. At one point it was neat that they got a second shot at Wheelie and made a full transforming figure out of him at that "right" price point. But even that figure was doomed to redundancy because of course they'd make a Deluxe out of Wheelie just like all the other minibots.