Perhaps there's a case to be made that these older songs are still listened so much today, even by those who weren't alive back then, because by some abstract measure of soul satisfaction they were better? I'm careful with this hypothesis as I don't want to be unfair with newer generations of artists, but I don't think it's so crazy to consider either.
For example, the last 10 years or so have been greatly influenced by social media and fear of saying the wrong thing and being "cancelled". Of voluntarily silencing ourselves. How wouldn't that impact the artistic output of this generation? Couldn't this be a reason for a lot of modern music "lacking a sense of personality"?
I feel with social media we have gone pretty far into investing in appearances alone, and I think I'm not alone in this belief. Maybe the next years will be marked by more and more people sharing a wish to return to the overlooked authenticity which we used to call "art with a soul".
One thing I'll add is that we're at our greatest point of exposure to the worst music of our era. Every era has a surplus of low-quality, unoriginal, or maddeningly trend-focused music that gets a lot of exposure. In time these lackluster records will be filtered out and mostly forgotten. In time people will look back on this period with a fondness for the great songs of the era that have endured and forget about the works that failed to differentiate themselves.
As such, it's easy for us to look back on the music of the last 70 years and think that things were better then because we don't have daily exposure to the lackluster songs of those past decades.