I think one of the problems is this: NO ONE ever posts "Wow! my pup is just the healthiest li'l thing goin'! She *never* has any problems and can eat anything she wants"
Nope ... doesn't happen. What DOES happen is that someone has a pup who has problems - who then posts to get support, help, and opinions. You don't need to do that with a healthy pup, so the only ones you hear about are the ones with problems.
Yorkies are a toy breed: they're tiny and more prone to injury. But all breeds have problems - even the "mutts". Read any breed specific board and you'll find the threads filled with problems ...
My two babies came from different breeders, neither one of which would be considered "good". But they were caring individuals who allowed me into their homes to see how the pups lived - and it was good. They were loved, at least. They're both just over a year old, and so far are as healthy as they come. But I also make sure that they're fed as well as I can possibly supply.
When I first got them and read all the stories, I wondered if I'd ever sleep a whole night again without checking on them
. But they're fine.
I think we think they're so "fragile" because we only hear from the folks who have pups who ARE fragile. But they're not all like that, not by a long shot. If they were, they'd hardly be as popular as they are: no one could afford to have them.