I highly doubt the increased mp cost is directly responsible for people not playing or will cause incoming players to turn away. This is just as ridiculous as claiming that anima will cause people to turn away. No single issue of that sort is going to so easily turn away the average player.
As for the notion that 1.18 somehow made it "too difficult" to solo... i havent had any issue soloing. You just have to be smarter than the average mob