I think if you read enough reviews of anything, you're going to see enough negative opinions posted by some very particular travelers. PH Washington, as the OP says, is not up to par with some other PH properties we've stayed at (Vendome, Tokyo, Milan, NYC, Chicago), but its certainly a nice hotel with a great restaurant. One issue with social media and the modern day internet and information age is that its info overload and you gain access to information, reviews, blogger comments, etc., from people that may be judging the hotel based on thousands of stays at many many hotels and have developed very specific needs and tastes that make them comfortable or otherwise happy. Having said that, and respectful of all of those reviews, a normal or average traveler will experience luxury at any Park Hyatt that is above most hotels and of course our average lives.
We also have future stays booked at PH Sydney, Melbourne and Palma Mallorica. With plans to hit Toronto, Colorado, San Diego, Los Angeles when it opens and St. Kitts time permitting.
We're a big fan of the brand, luxury and level of service at any Park Hyatt.
Thats my two cents.