It would be unfair to say that there is no good new music. Just as it would be unfair to say that all music from the 60's and 70's was worth listening to.
That being said, it is not a coincidence that most of what played on FM radio and streamed is older music.
The reason is simple. It is better music.
In general.
It is more emotionally engaging.
It has more to say about real life, love, and the human condition.
It has more dynamic range.
It is played my musicians playing actual instruments.
It has more variety. Less formulaic.
Case in point. The top albums of 1971. No two similar and all fabulous.
"Hunky Dory" David Bowie
"Led Zeppelin IV" Led Zeppelin
"Blue" Joni Mitchell
"Tapestry" Carole King
"What's Going On" Marvin Gaye
"Who's Next" The Who
"Sticky Fingers" Rolling Stones
"Meddle" Pink Floyd
"LA Woman" The Doors
"Fragile" Yes
"Ram" Paul McCartney
"Aqualung" Jethro Tull
"Live at the Fillmore East" Allman Brothers
"Santana III" Santana
"Every Picture Tells a Story" Rod Stewart
"Madman Across The Water" Elton John
"Songs of Love and Hate" Leonard Cohen
"Pearl" Janis Joplin
"There's a Riot Going On" Sly & The Family Stone
"Imagine" John Lennon
"Killer" Alice Cooper
"Master of Reality" Black Sabbath
This is just one year and it was all played on the radio.
It is a big reason why we are still listening and still buying gear and music.