The reason GM engines are failing is because the engines were rushed to market and blew out head gaskets and broke head bolts.
The under designed fuel system would also rust out from the inside.
Some of the GM engines also had lifter failures and crank bearing problems.
Lifters in some GM engines also collapsed and sometimes push rods would bend.
The GM 6.2 engine had a bad batch of lifters and main bearings and it's being remedied.
Crankshaft Misalignment is also another cause of GM engine failures.
Without the proper support from the bearing the crankshaft could become misaligned and cause uneven wear of the bearings.