GM was at its best when the divisions competed hard against each other in the 50s and 60s.
If something was messed up (styling or engineering), it was confined to one brand.
Once they went to "corporate" platforms and powertrains, screwups were mass produced by the millions, across three or four or five brands. This was the legacy of Roger Smith.
How can they compete against each other when the UAW runs the show, then and now?