This was a very interesting read.
As for individual intelligence gaps, and specifically animals, I would say it is still pretty comparable to humans. The difference being the intelligence levels each species are working with. For instance, Ive met a lot of dogs. Some of them actually surprise me with how smart they are, and other dogs are just dumb but adorable animals. Same for mice and other rodents. And same for humans.
Humans won the evolution lottery in relation to industrial and cognitive ingenuity, and when we try to compare ourselves to other animals it seems like there is a shorter gap between different individuals intelligence’s in a species. However it probably scales the same down.
As for the rest of it I relatively agree. Thinking about how different potentially technological mature species get there was quite fun as well.