It's always been complained, I suppose because it's easier to remember the
favorites of a past period than wade through the current batch to find them. It
doesn't help that popular music is mostly a youth market which is less experi-
enced.
In the early 1900's, popular music wasn't as serious as classical music. In
the late '50's-60's, mainly more conservative older types and acoustic jazz fans
complained (you used to have to know how to play an instrument). George Martin
once wrote that many older people first heard the melodic sensibility of the
Beatles with "Yesterday" because the instrumentation had the acoustic sounds
they were familiar with.
In the 70's, people complained that music started to seem more produced and
processed--drum machines, etc. The sounds haven't changed much since but that
makes it easy to detect regurgitated formulas. Some new sounds like vocoders
beg for complaint.
At the other extreme are the trendy fans. Sydney Harris once wrote that
they're ironically the most dated: they restrict their favorites to a narrow
band of the latest dates.