Bold: Shiryu may not be able to do exactly that, but whos to say he couldn't just blitz and slash Blackbeard and his whole crew like he did those ID guards. The BB pirates were underestimating Magellan, Shiryu would have capitalized on that as well.
1st red: Ace never nearly killed Blackbeard. How does Blackbeard getting hurt by Aces attacks mean that Ace almost killed him? Either could have won based off what? Blackbeard had the advantage the whole fight.
2nd red: Two years later yeah when Ace is dead and Sabo had time to keep improving. Two years ago who was to say Sabo Haki was good enough then? Aces fruit gives him advantages Sabo does not have.
1st Blue: But its YOUR logic. You say Sabo should be above Shiryu by past battles and feats, but if you believed differently then why in the hell are you saying Sabo would mid diff him? Because after all, someone stronger two years ago doesn't have to be stronger still. Right?
The hell is this BS? It has plenty of merit because whether or not Magellan beat Shiryu they were said to be equal in power. Have you never heard someone say X beats Y 5 amount of times out of 10? Ace=Marco was the worst example you could have used.