In the Middle East like China at first only the truly wealthy were able to stay in 5 star hotels when the chains went international - the result was guests wanted true luxury like a RC or STR.

Marriott made its name by being bland, conservative and all about reliable execution and points - perfect for road warriors in Arkansas or Arizona but exactly the opposite of what the newly rich in the Middle East and China wanted. So few developers wanted to flag and invest in the Marriott brand. It just wouldn't draw crowds. They didn't and so the hotels are old and cheap and for price sensitive customers or tour groups.

I stayed at a Marriott once or twice before the SPG merger and hated the cookie cutter aspects and relatively few suites. Since the merger, the only legacy Marriott brand I've been happy with is JW which I actually really like. I've been disappointed by every legacy Marriott brand I've stayed at aside from JW.

Being one step below true luxury but luxurious enough, my best value stays have been at JWs where mgt has gone out of the way for me. It's similar to Hyatt Regencys - I'm usually a Park Tyler but some HRs have been incredible to me
I should add, grand Hyatt faces many similar issues to Marriotts in China. They went in early as pretty luxurious for the time, but have been superseded by other luxury chains. Grand Hyatts re usually old, and just not great in the China market. Give me a HR and PH over a GH in 99% of cases in China