In my eyes there cannot be balance in the force whilst it remains one-sided. Eradicate the Sith and all you have is a 100% light side imbalance.

I hate to bring the sequel series into things but actually if we are being honest (about a fictional universe) then ultimately Anakin did bring balance because through him Luke was born and Luke tore down the remnants of the Jedi order himself and trained Rey to not bury her darkness but to accept it.

Had ROS had better writers we might have had a complete eradication of the Jedi and the Sith and a new order spring up who taught that light and dark and 2 sides of the same coin.