10 teams make the playoffs nowadays. The Mets have some good pieces. If they sign an outfield they could be interesting to watch. Regardless, the idea that if a team isn't a championship contender they're excused from making any effort to improve is nuts.
MLB is not the NBA or NFL where moving up a few positions in the draft makes a difference. Look at the list of perennial contenders and you'll find very few have gotten most of their key players by tanking whole seasons.
StoicSentry's analysis, that it'll be impossible to acquire all the pieces you need in a single off-season and some will need to be free agent signings, makes more sense.
The Mets have some good pieces? Like who? They just dealt their ace pitcher for top quality prospects. We have an all-star 3rd baseman surrounded by mediocrity. Ike has potential to be an above average 1B if he hits lefties better and plays the way he did in the 2nd half. We have a solid rotation with question marks in Harvey, Niese, Gee, and maybe Santana. That's it really.
Murphy is not the answer at 2B, Tejada is a good SS but doesn't provide much with the bat, and the outfield on paper sucks. Our bullpen right now is pathetic, so hopefully that improves. There was no one we could have gotten to make all of our holes better long term. D'Arnaud gives us some hope at catcher, an offensively scarce position. There are some intruiging outfield options for next year, and maybe a 2B to replace Murphy.
The higher the draft slot, the more options to choose from. The cumulative WAR within the Top 10 is better than the rest historically for the most part. It makes a difference, and having that Top 10 protected pick means you can go out and sign multiple top free agents without losing your first pick. That is perfect for a rebuilding team trying to compete without sacraficing top end talent.