1) If you create a system that few people that know the game actually know about, that's a problem. So step 1 is conveyance. Increase the understanding. Make your client side download teach people short and sweet how the new system is, how it works, why they should want to get involved, etc. With steam this should be extra easy.

2) If you create a system that only few people benefit from (the top... let's say 25), then few people will care. Where there are millions of players excited that they went from Bronze to Silver in League of Legends/Starcraft II or Silver to Gold in Counter Strike: Global Offensive, those small but gigantic land mark changes don't exist as of yet to appeal the other 500 players who are never and will never be good enough to play in the end of the month tournament. Find a super small way to reward players and excite them along the way that this time they got to rank 1,000 instead of 5,000 or 800 instead of 1,000 and you'll hook people in. Preferably a way that doesn't destroy the economy.

It's worth mentioning that this ranking system is by far the best one Toribash has ever had, so kudos to every involved in making that happen.