A little of topic, but I think...
...that's not true. The Republic did stop the Empire's advance in the midrim. The Empire changed it's tactic by including Mandalorians who blockaded crucial trade route(s). After the Mandalorian Blockade was broken, the Empire had basically lost all it's advantages and was on even match with the Republic. In this situation Revan could convince the Emperor to seek peace (which included sacking Coruscant during the negotiations to get better terms).
IMO without the treaty of Coruscant we would have a decades long war of attrition which would have wrecked both, Republic and Empire.
(But, of course, the Republic wasn't weak at the beginning of the GGW.)
That's not what Revan said.