Thats really far off. "PtW" screwed up MP true, but Warlords did the same with its touted vassel add-on. MP was a add on play mode and was seprate from the essence of Civ's great Epic game that thrived on deep campaigns. It never distracted from the core 1 player expeirence, it supported it. What makes PtW win this comparison is that it actually enhanced the performace of the core game with dramatic turn speed improvements, while letting you go 'real world' size and selection for once.
Vannila 3 was a mess, much like Civ4 when it came to the 'go large' possibilties. If you read the PtW change log it cleary states performance upgrades. It ws more annoying in-game lag instead of between turn, that was CIV's worse problem and it was never addressed when they bulked it up with Warlords. This is worse IMO.
Play the World made it actaul feel like an expansion in every sence if you know what I mean.
The new victory conditions were especially cool. The king units was a big step in replay value.

but its the fact You needed it ("PtW) to maximize your game enjoyment, thats what really can't be said the same for Warlords