Fine Akbar. Here's my god reason. Yoda SAYS he can't beat sidious. In the novelization of Episode III. I'll give you a damn excerpt! So Yoda and Plo Koon would get beaten BADLY!
"It Came when Yoda found himself alone in the against the dark. In that lightning-speared tornado of feet and fists and blades and bashing machines, his vision finally pierced the darkness that had clouded the force. Finally he saw the truth.
This Truth: that he, the avatar of light, Supreme Master of the Jedi Order, the fierces, most implacable, most devastatingly powerful foe the darkness had ever known...
just-
didn't-
have it.
He'd Never had it. He had lost before he started.
He had lost before he was born.
The Sith had changed. The sith had grown, had adapted, had invested a thousand year's intensive study into every aspect of not only the force but Jedi lore itself, in preparation for exactly this day. The sith had remade Themselves.
The had becomenew.
While the jedi-
The jedi had spent that same millenium training to refight the last war.
The new sith could not be destroyed with a lightsaber.........etc etc...
Hmm, Yoda thought. A problem this is..."
There You Go Akbar.