The miserable Crowne Plazas are generally the older ones. In the US many CPs were built in the 1980s. Today they're showing their age. Many properties have been renovated in the past 5 or so years with new carpet, paint, and furniture. These updates help but only to a certain extent. Look closely and you'll see the hotel is still a not-particularly-high-end physical design from 35 years ago. The phrase "lipstick on a pig" comes to mind.

In other countries, particularly in booming Asian countries, most of the CPs were built much more recently. Thus they have fresher designs and materials. And they were also designed to compete with higher end alternatives in their markets.