Occupancy rates are much higher than in 2008-2009 plus you have plenty of folks on free credit card nights - this is probably the main reason. If Hyatt does rank diamonds it would only come into play if they have to choose which one to upgrade when they have to pick one - i have no reason whatsoever to believe that diamond "grade" would be considered to treat you differently.
A lot of people feel that the benefits are not what they were a few years back on UA, SPG, Hyatt etc but the market is different now and expecting the same freebies is unrealistic ($100 resort stays with $100 meal voucher - good days). On the other hand the rates are much higher so i get a much better value out of awards now vs back then.