6. A lot of classic, old-school hip-hop sucks.
Well, a lot of hip-hop sucks, period—but we all knew that the 400th iteration of the Lil Jon formula was probably a bit much back in 2006.
The over-the-top reverence for the old-school era or, later on, hip-hop's golden age, means a lot of middling iterations of classic formulas have snuck into wider knowledge. There's even a faux-record-collector genre ("random rap") named for otherwise-forgotten tracks from a particularly celebrated era in hip-hop's history.
Even for tracks that were important, being significant doesn't mean they will appeal to younger audiences down the road. A track could provide the home for a groundbreaking new technological advance, a frequency filter, or a particular style of sampling, but if the song wasn't all that great, it might not translate through the generations.
Hip-hop, in particular—heavily referential, bathed in pop culture and era-specific slang and references—fights an uphill battle when it comes to maintaining lifelong relevance. While some songs sound as new today as the day they were released, others haven't aged quite as well. Sometimes it's a matter of a groundbreaking artist not influencing too many to follow in his footsteps; other times, it's the opposite problem, as too many rush to replicate a formula, obscuring its initial uniqueness. Hip-hop is a heavily contextual art form, and if an old head has to fall back on "you had to be there," then the song probably wasn't that great in the first place.
This isn't to excuse young people's impatience with the past. And of course, the rare song that feels at once unique, of its era, and timeless—think "The Message" by Grandmaster Flash, or "Beat Bop" by Rammellzee—will always transcend regardless.