I attribute the sound issues of brightness and sterility to be the fact that the DACs were still immature technology. Some of those early CDs sound pretty good on more modern players we have today.
True, but it was immature process as well. Some records, used to make CDs had wrong frequency correction - intended for LPs. In addition many records got digitized with less than perfect A/D clock producing jitter, that cannot be removed. The only way to remove it is to digitize again, if analog tapes still exist.
As for different volume - I suspect that "volume wars" were a necessity, since CDs were, because of size, widely used in boom boxes, cars etc. where full dynamics of recordings were not welcomed (buzzing speakers). Same way TV sound is horribly compressed since most of people used tiny TV's speakers.
SACD, intended for better reproduction, had ability to bring back full original dynamics, but greed pretty much killed the project. Todays LPs also carry this promise, but world also seems to go in the opposite direction with more people listening to MP3s.