He's also last in the NL in DWAR among qualified third basemen and was something like two up from the bottom last year. He's had a negative DWAR in seven of the last eight seasons. He was never a great defender, and now he's really old. Any fielding metrics that show him as a strong fielder in 2015 are either the victim of a small sample size or they are simply wrong.
For the people calling this a "great" move, you've simply got really, really low standards. It's an OK move, and the Pirates either had to make this move or a similar one, but at this point Ramirez is a well below average third baseman. Is he better than someone like Brent Morel over there? Sure. But not by some significant margin.
There is a reason that the Brewers took a non-prospect relief pitcher in return for Ramirez, and they also agreed to pay more than half of his salary for the rest of the season. Right now Ramirez has pretty much no value at all to anyone other than a team made desperate by injuries like the Pirates. And even with the Pirates being desperate and the Brewers being willing to pick up a large percentage of Ramirez's salary the Brewers still couldn't get even a decent prospect for him. If that isn't telling you something it's because you simply aren't listening.
The Pirates are hoping to catch lightning in a bottle over the next month or so, but if they don't they haven't given up anything significant anyway, so it's certainly worth a try.