I've played München Eichenried a few times and can confirm that although it's not a bad course for German standards, it is rather mediocre, especially compared to the average PGA Tour course.
I don't think there are that many great alternatives in Germany though, Gut Lärchenhof (Nicklaus) and St. Leon (Dave Thomas) are other courses in Germany that have hosted ET tournaments, and they are probably a step up from München-Eichenried, but still far from great. It would be a nicer, of course, to host an ET event at Hamburg Falkenstein, Budersand or even the Faldo Course at Bad Saarow, but I don't know how realistic or doable that is.
Concerning other ET events, I haven't studied the tour schedule yet but it feels to me that the courses are improving overall, such as the Italian Open being played at I Roveri or last week's Irish Open at Portstewart, which was a joy to watch.
It seems to me altogether that the spans of both quality of the courses and quality of maintenance are wider on the European Tour and more constant on the PGA Tour. I guess it's really a matter of preference for the pros, some surely like it more varied and not always prefectly manicured, others surely don't.
As has been said, there is definitely most of the very good courses in each country left out on the schedule and there is a lot of room for improvement concerning the courses played, but the answer to why that is is pretty simple and has already been said: money