Dolby Deterioration

It’s my belief that recordings made in the 50s and early 60s, before the advent of Dolby, sounded more open and detailed than records made later. You can here the difference even in digital transfers of the earlier discs.  I’ve maintained this for many years.  I wonder if anyone else has noticed this phenomenon.  
Adding to the further deterioration, was the trend away from tubes to solid state equipment.
its a pleasure to hear pre solid state, and especially pre Dolby presentations.