They've never really much emphasis on the Warlords powers just their reputation.
Moria is a man who once fought equally with an Emperor. That may be the only bit of info the average citizen or common pirate know about him.
Hancock is a leader of female man-slayers who leaves any ships' she encounters adrift due to the crew being turned to stone.
Mihawk is the acknowledged as the best swordsman in the World Greatest Swordsman meaning every scary marine with a sword they've ever met or heard of isn't as good.
Jinbei is the leader of the Fishman pirates and likely the strongest Fishman, a species that are probably greatly feared as monsters by normal pirates already.
Kuma is known as a Tyrant who has committed every atrocity a pirate could commit.
These reputations gain even more weight when pirates attain more knowledge of the seas dangers on their travels. What these pirates abilities actually are is almost irrelevant. The deterrent comes from the fact that out of everything pirates may face while traveling the Grand Line, these guys are supposed to be even worse.
I was agreeing with you, in a rambling way. He's not weak at all but I want him to flaunt his powers a bit more.
The problem is the utility and function of Moria's Powers–they do not allow for flaunting. His powers are more for reconnaissance and strategy, not overwhelming power and massive retaliation. His powers are precise, the other Shichibukai's powers are (seemingly) more geared towards destruction and get the job done. In fact, the only move he showcased that was geared towards destruction was Shadow Asgard--which in turn caused him to lose control of his powers and mind--which shows us the audience that his powers are not meant to be flaunted in ways that some of you want it to be.