Wrong. Don't ditch it the moment you enter Sen's Fortress, you should keep it depending on your build. Like for low str it can be good and it's still one of the best swords despite the no scaling. What I did on my first playthrough was grab two Dragon Scales then upgraded the drake sword to 240 Atk and Sen's Fortress was a cakewalk. Wait for the Silver Knight Straight Sword then farm some Twinkling titanite (10) and the sword will serve you well, well indeed my good friend. Well indeed.