GMT800s were very competitive for their era, but vehicles just get better with time. The biggest improvement by far was rack-and-pinion steering. The old recirculating ball setup was past its prime and annoying to keep tracking straight on the highway. Many GMT800s as well used the 4L60 trans, which really didn't like towing and was a known weak point. Interiors too were a major change. IMO K2s have the nicest interior GM ever put into a truck. The GMT800 interiors were about what you'd expect for a domestic truck from that era, but man, the pre-2003s were pretty spartan. Basically a carryover from the GMT400s. I've never seen a GMT800 in the last 10 years without rips in the leather.
Taken in context, the 800s were good competitive trucks for their time, as are/were the K2s.