Every year they put off a QB Nelson, Leonard, and Moore are getting older. Waiting until next year you don’t know what will be there or where you are picking. If the right guy is there now you take him. That is the most important piece.
I don't think this team is that far off. I think we have a ton of good players and I think we have a ton of solid to very good YOUNG pieces that can only get better. The problem is the little that we are missing is missing at some of the most important positions in football - namely QB, OT(if AC retires, and even if he doesn't we will need to find long-term replacement if he's thinking about retiring now), WR(both to supplement TY and to eventually replace him whenever he's gone/retired.
Its going to take several years to build this team. Look at TY and AC having to be replaced. You need those kinds of players anyway. Nothing says that you have to start building with the QB and wait on everything else until you find him.
Marvin Harrison didn't explode until PM cam on the scene, true, but he was here and that certainly helped PM. MH did well in his early years with Harbaugh.