Balloon body, short body, mutated parrot mouth, are all the same undesirable traits to me.
They may be cute to some, but is cramming a bunch of organs in an un-natural way, in too small a space good for a species long term?
Or simply trying to achieve certain colors, a big knot on the head, that may be bright or distinctive, out front, but sacrifice genes for robustness instead.
Look at the average EBJD, or most line bred Rams, would you consider them robust?
Most die if you look at them sideways
But even with hybrids, all you can really see, is visual shape and color.
What you can't see, are the genes that may be scambling in undesirable ways.
A certain species of fish may have evolved abilities to withstand specific environmental changes, (cold/hot/less oxygen, heavy flow) sacrificed, when bred with another species without the natural gauntlet of survival of the fittest test given by nature, these robust genes go by the wayside..
Consider that the propensity to get Columnaris was once known as "Flowerhorn" disease".
Although the disease has been around for years, in a moderate way,
once FHs became popular, it has seemed to increase in epidemic proportions.
Just coincidence?
Back in the 1950s, and 60s, Columnaris was dubbed "Live Bearer"disease, and occurred when it was popular to randomly cross breed live bearer species.
Another simple Coincidence?