Really? Nothing has changed, only the definition of "good oldies". When I was a kid, commercials were using Perry Como and Joe DiMaggio to hawk their goods. Edward R. Murrow smoked on air as did Carson and everyone else. Harry James was held out as the ultimate trumpet player even though Miles and Lee Morgan were considerably more important not to mention Clark Terry was technically superior to them all from a proficiency standpoint.
Commercials and film always dig deeper to find tracks that evoke memories from their target market. The "Summer of '42" wasn't made in '42. The pharmas are the worst, I hit mute on the TV when a drug commercial comes on since I know they will butcher an Earth, Wind and Fire's "Let's Groove" or Fleetwood Mac's "Go Your Own Way" with new lyrics. 40 year old tracks. You still hear Glen Miller music on some commercials. Hip hop sampled Aerosmith...music evolves. One generation of music may be more relevant to you but it doesn't make it more relevant in general terms. Another reason certain tracks get repeated over and over in TV and Film is due to who owns the copyright. That's another discussion for another day (Motown especially).
People lament that bricks and mortar are all but gone but selection was limited to maybe 4 or 5 major brands across the 2 or 3 stores the average town might have that you MIGHT be able to call audiophile. The DIY/mail order was available in the backs of magazines which is where the real innovation was ocurring. We might extrapolate that the DIY/mail order side of things is actually how we have evolved...consumer direct has grown and retail has contracted. @elizabeth mentioned earlier in the thread that she got hooked on music through the classical music she received in the mail. Now its all streamed and widely available instantly but there are still people getting hooked on good music.