problem with the doodle crosses is that there is no standard or conformation that breeders are working toward

In many cases, because there are certain specific standards that breeders want for purebreds, they end up using the same stock a lot and creating other issues... (the bulldog being the most prominent, but not the only, example - see https://www.thecut.com/2016/07/weve-run-out-of-time-to-save-the-bulldogs.html)

There's advantages to purebred dogs for sure (especially if they haven't gone so far down a path to effectively breed out that genetic diversity), and there's advantages to mixes as well.

Ideally, you end up with somewhere between the extremes - they shouldn't be just throwing random dogs together with no thought for outcome... but they also shouldn't be so tightly constraining and min/maxing certain outcomes that the dog becomes a caricature