This is an interesting position: the Greens and the Left have the right crisis diagnosis, but they need the weight of the macroeconomically clueless SPD in order to make a viable (seats-wise) governing coalition

Yes, and a pony too, please. The trouble with the SPD is that their election results are still too good to support a change. They need the educational effect of getting far less than 20% before they start to debate a red-red-green coalition. And by then it will be too late.