As someone who has had many mutts and rescued purebreds…
I’m assuming you don’t know what you’re doing if you think all mutts are difficult. Generally, people don’t exercise their dogs enough and then run into problems. Doesn’t matter the dog, but a consistent routine of lengthy walks and runs has never failed.
#1 was a half-chow nightmare from Hell (yes, I was clueless) but the next three weren't problem dogs, just difficult to understand. Conventional wisdom did not consistently apply across the three.
It was like multiclassing three characters in an RPG you don't even know the classes of.
Unlike purebreds. You can literally buy an instruction manual for your specific breed. Way easier.
What works is having a test-period before changing ownership. There can be many reasons for incompatibility, and often quite unfair to blame it on the dog who had no say.
And if you don’t have time, don’t get a dog.