> I have met two 'newfie poos' as they seem to be called and wow, what a handful. Not sure whether it was down to the owner or the mix of breeds
While I would hesitate to use the phrase "dumbed down", there is a good reason why the giant breeds of dogs have been selected over time to have calm placid temperaments. There are records from the USA in the 19th century of Newfoundlands attacking and killing humans, as they were once used as guard dogs.
Mixing the modern day Newfoundland with something as exuberant as a Poodle is bound to lead to difficulties, and not only with the acres of coat that would need specialist attention.
Form and function yet again.... A giant breed of dog, most commonly kept as a companion dog nowadays, must be calm and biddable enough for its owner to control it, and have a coat that is easily cared for without any major remodelling.... It's one thing thing taking a Poodle in for a regular clip and trim, but a dog that big needing the same would be a groomer's nightmare.