Ace was the 5th strongest WB Pirate. How does current Luffy, who will become admiral level in a few arcs, being stronger than Ace mean that the WB commanders weak? Ace has no feats what make him equal to Luffy.
I don't know why you think he was the 5th stronges. All of the whitebeard commanders seem to be ranked according to how strong they are.
For example, Marco was stronger than Jozu who was stronger than vista and so on. In that way Ace was the second strongest commander.
Let's talk about feats,
Ace fought like a beast with a Yami BB, who even before acquiring the DF power was strong enough to give shanks his trademark scar, which shanks made clear happened when he was fully serious about the fight.
When Ace and Luffy went up against Aokiji, Luffy was saying something along the lines of
"Someday I will be even stronger than you ace"
And Ace, "ok, but for now I will fight the admiral and protect you". That shows that Ace had enough trust in his strength to take on an admiral.
Certainly if Ace was the fifth strongest Aokiji must be extremely weak.
And if you want to talk about the natural weakness of Aokiji to Ace's fruit then that applies to his fight with Akainu as well and it still went on for 10 days. So, Aokiji understood that this battle would take sometime to end he stepped back.
At least, this is what I think makes Luffy atm tie with Ace because of his position as the WB pirates 2nd division commander.
