People hate stupid changes.
Stupid changes are subjective.
people seem to hate changes in general.
I don't get how anyone can say that the new UI is worse than the CoH1 UI.
it might not be perfect, but it is a huge improvement. (just take an objective look at the comparison thread on these forums)
People that wanted COH2 just to be a graphics update, would probably say "gosh, CoH2 is just a graphics update, damn Relic, be innovative once!" if it would only be a graphics update.
A sequel should change some stuff or else it is not worth making a sequel in the first place. (in the aspect of fun, financially it might work, just watch CoD... people buying the same game every year for 60$, with no real changes... for what? Nobody knows, most are disappointed after playing for a few days).
edit:
Also, i could bet on that if the gameplay in CoH1 would have been the same as in CoH2 and CoH2 would now change it to the gameplay from CoH1, the same people would complain