I think there is a load of subtlety that people have missed in TAE
I think there is a fine line between subtlety, obtuseness and actually just unclear writing. The subtle elements are things people will be arguing about for years, but there's also stuff that is just not parsed very well (I get the impression that, with his old editor gone, TGO and TUC suffered from a lack of outside editing by someone really well-versed in the series). The ending of TGO suffered from that but there's a lot of it in TUC as well.
I think the general reaction to TUC is a lot of people impressed with how deep down the well Bakker went, mixed with bafflement at how much stuff they thought would be resolved but wasn't even addressed.
The other main complaint I've seen is that:
People wanted to see the Consult in their full power and get a good grasp of what they were up to. The revelation that the Consult is ancient, broken and pathetic, easy prey for the Dunyain, I think works really well on the level of intelligence and art, but on a more emotional level spending seven books building up the Inchoroi, the Consult, Aurang and Aurax, hinting at their power, naming the last book after them, and finding out they've been pretty much destroyed and conquered completely off-screen really didn't work as well as it should. It can't help but feel anticlimactic, although there is scope there for an Atrocity Tale showing the subversion.