Is there a narrative why Garp could rival guys like Roger but none of the Admirals can't rival Shanks?

It's obvious been very interesting to me how there is no a single marine in the modern era that can rival Shanks while Roger had Garp who was on par with him in strength. However, not a single Marine has been portrayed relative to Shanks, neither if we use portrayal or we use feats, not a single Marine is truly on his level.

Like if we go by portrayal it's not close. The 5 Elders thinks Shanks is unstoppable if he is angry, in Marineford Shanks was able to stop the war with 3 Admirals and in Wano we saw Shanks show a massive gap with an Admiral

And if we go by feats it's not close. No Admiral have shownn to be capable of Sky Splitting, Shanks defeated Loki which no Admiral could defeat in 8 Years and Shanks No-Diffed Kid while we saw Admirals not having an easy time with Admirals in the Marinford War and we even have an statement of Marco being equal to them

Like hell, even Ben Beckman might be stronger than the Admirals, given that Oda himself implied that Beckman's Haki si superior than that of an Admiral which automically means not a single Admiral is any type of threat to Shank's

Like hell, Garp is the only Marine who has Haki on par with the strongest Pirates like Roger, WB, Kaido, Rocks, etc, that's very bad on the Admirals portrayal.