I understand the anger, Yankees fans. After witnessing Stephen Drew hit .162/.237/.299 (44 wRC+) and put up an absolutely dreadful -1.1 fWAR in 300 PA in 2014, I can absolutely understand why you'd be miserable to see Drew suit up in pinstripes again.
I'm not going to try to convince you that Drew is some heavily undervalued player. What I will tell you, which should make you feel better, is that this is perfectly adequate in length and size. Steamer projects Drew to hit .219/.295/.353 (82 wRC+) with 0.7 fWAR in 105 games. That's pretty blah. It's actually eerily similar to Brian Roberts in terms of projection, but I'll get to why that doesn't matter as much in a bit.
An important point to note, though, is that the projection may not be wholly accurate. His 300 PA with both the Yankees and Red Sox were pretty darn bad, but not only does 300 PA not a player make, but keep in mind his irregular spring training schedule. I'm not well versed in how one's timing can be affected by not seeing professional pitching for a stretch, but it's safe to say that taking batting practice for nearly seven months doesn't bode well for the following season. I would guess that the first 100-150 PA were spring training quality, and then he just hit a heck of a slump. I'm not going to go as far to say that he is as good as he was in 2013, but I doubt he is as bad as 2014, too.
As many on social media have already pointed out, this signing wouldn't bother most if the Yankees didn't have a habit of sticking with veterans over anyone else. That's certainly a valid complaint. The team once stuck with Tony Womack at second base until bringing up Robinson Cano back in the day, and they have done it again with Chris Stewart and Brian Roberts over the past couple years. So yes, I can see why fans would be wary to hand Drew the job because the team may leave him there no matter what.
Thankfully, the Yankees are lucky enough to have backup options. It's clear that the front office has little confidence in Rob Refsnyder's defense yet, and they clearly (rightfully so) don't think that Jose Pirela is an adequate second base beyond his role as utility man. Frankly, I don't blame them there. Sure, Refsnyder has torn the cover off the ball in the minors, but I still trust their internal analytics and scouting reports in regards to current talent, and especially defensive ability. If Refsnyder is truly the better player, then he will get a chance to play. He is also not so terrible that if Drew imploded, the team wouldn't be wholly uncomfortable giving him a shot. It's not like in the past where they would have to hand the job over to some unknown organizational depth piece; they have at least some options to fall back on.
There is a good chance that Drew will be pretty mediocre, but there's also a good chance that the internal options would be poor as well. And what would the team do if the internal options implode? They'd be stuck. At least now they have an actual major league baseball player who could hold down a job, hopefully. If he is terrible, then he will get his ~200 PA like Alfonso Soriano, and then pack his bags. If he is adequate then he makes his salary worthwhile, and they give themselves more time to develop Refsnyder's defense.
There are very few one-year deals, especially at this low a cost, that are bad deals. It certainly makes the Brendan Ryan signing a real head-scratcher, but this deal on its own makes enough sense. There is an obvious concern that second base could be a black hole, and this deal at least decreases the probability that it will become one. For just $5 million, I'll take my chances and see what Drew can do. If he is terrible and the team doesn't replace him, then the larger concern is that both Refsnyder and Pirela are not competent enough to handle the position because Drew will not "block the kids." My fingers are crossed that either Drew is adequate or Refsnyder wins the job on his own merits, but I'm not going to hold my breath. Take this deal for what it is, Yankees fans: depth. It won't hurt as much as you think.