I think because the flaws with the Euro that have been very disadvantageous for Greece are for the same reason very advantageous for Germany. Germany gets to have a big account surplus with a relatively devalued currency.

She may be doing the wrong thing for EU, but the right thing for Germany. In the long run perhaps the right thing for EU is the right thing for Germany, but I don't think German voters see it that way right now.

She is still in office because she hasn't done that many unpopular things, especially in her first 2 terms. If anything, she is as seen as to inactive, but as long as the status quo wasn't too bad... And internally, many see her having a lot of influence on the EU as good.

The general opinion is not a fan of "Mommy Merkel", but it hasn't been enough to propel the actual alternatives from the corners to a position where they can't be ignored, especially since right now the two largest parties (Merkels CDU and the SPD) support Merkels government together. Traditionally they'd prefer partnering with a smaller party, but their preferred coalitions didn't work out. The alternative combinations that would have had a majority are not seen as viable (yet).

And sorry, this isn't great for change, but doesn't make Germany non-democratic. Other possible governments after the last elections would have been more interesting, but I'm not sure if they would have represented the votes better.

Right now it seems like opinions drift away from Merkel in both directions, so it'll be interesting what happens next year. Election campaigns haven't really started yet, so it's hard to judge how the large parties are going to position themselves. SPD has to do something to break out from Merkel, or work another 4 years with her.

German quality of life is the best it's been since unification, why would Germans want to get rid of her?