It’s nice to see someone arguing the nurture side of things. Breed does have a significant influence, but how a dog is treated makes far more difference to their eventual personality.
I have always talked to my dogs the way I would talk to a human. I don’t use babytalk or even adjust my vocabulary. Not only does it seem to give them a startlingly good understanding of human language, it also makes them more inquisitive and more interactive. If you treat them like people they behave more like people.
I have had dogs that were smarter than others, but the average has been far higher than people generally assume.