Being that you and I are talking to each other by forming thoughts in meat that us causing other meat to move around tells me that digital thought still has a lot of scaling room ahead of it.
Maybe superintelligence isn't possible for some reason, but the fact we exist should tell you that general intelligence is not magic.
The world created by human thought has given us such excess means of power production that we have literal gigawatts of electricity we can use in a trade off where it doesn't take us 4 billion years to make efficient circuits.