Perhaps in the lower levels of the Order, but masters on the Jedi High Council would be familiar with all the lightsaber forms and exceptionally powerful in the Force. They would not have become complacent in any areas. Even so, being able to kill a Jedi High Council member in a matter of seconds is impressive no matter what the era or skill of the Jedi.
They may thrive in other aspects,but combat speciality is not one of them.It is said many times that lightsaber dueling after the Ruusian Reformation was on a decline because the jedi faced always blaster weielding opponents and not force users and lightsaber users.So they became complacent ,ripe for the plucking by the Sith Grand Plan.
I think you overestimate Kit Fisto and the other jedi because of some kind of SW movies fanboyism.
Not that they were weak in anyway, becoming a Master in any era requires considerable skill - Kit Fisto for one managed to hold his own and almost defeat General Grievous and Mace Windu, well Windu invented his own lightsaber form. And Yoda had 900 years to master every single one, he was praised by many as one of the most powerful Jedi who had ever existed, and yet Sidious matched his power.