But you don’t automatically get rid of the health issues by cross breeding.
Cross a pug or frenchie or anything else like that and it might be healthier, but it might not - because those issues are not a single gene that you can breed out by crossing with an unaffected dog.
Some of the most common crosses are between dogs that share the same health issues, so they’ve just as much chance of getting them as if they were pedigrees.
The way to improve health is to carefully breed healthy functional dogs that have passed health tests, something that is very very rare with people breeding crosses.
The fact that some breeds are in a terrible state and shouldn’t be being bred from if you’ve any ethics doesn’t automatically make a labradoodle, cockapoo, jug or whatever cross is currently popular any healthier than it would have been if the breeder had bred 2 random untested pedigree dogs, in fact that what they are doing, they’re breeding 2 random untested pedigree dogs together, just not of the same breed.
There are some breeds that could benefit from outcrossing, but they’re not the ones people are commonly crossing.