Not at all!
Lucario cannot do much damage to Cressila without Crunch. He only has room for FOUR MOVES. Let's look at them...
Close Combat is his main STAB. That stays.
Swords Dance is needed as well.
Without Extremespeed, Lucario gets revenge killed easily.
That leaves one more move availible.
Crunch is almost necessary.Without it, he gets walled by pokes like Cressila, Dusknoir, and other bulky Psychics. But he is stopped by Bulky dargons & Gya.
Stone Edge helps take on Gyarados, or even Mence. But it STILL leaves him walled by Cressy, etc.
No matter what you use, Gliscor stops them all. But...
Ice Punch beats Gliscor. You are now walled by Gya, Cressy, Noir, etc.
Thunder Punch helps to REALLY beat Gya. Great for teams that is really weak to Gya, but useless elswhere.
No matter what, ygou are still stopped by Weezing & Spiritomb.
So how is it so dangerous? The only problem is that Lucario is a dangerous switch in, as you don't know what it has, but it is in no way uncounterable.