Well, the class E problem starts with the fact that class E cannot be avoided in germany. Every airspace above 2500 ft GND or 5000 ft, whichever is lower, and belo FL100, is class E. Lower around airports. And not only glider pilots like it that way, pretty much all private pilots in germany, no matter which type of aircraft they pilot, like that they can freely fly in that airspace without the need to talk to someone. Not to mention the military, they love it too as they mainly fly VFR with their fast jets. And only some of them need a transponder.
Now, the main issue is of course the airspace in the approach and departure path of airports with IFR operation. And that airspace gets evaluated every year and adjusted based on airspace user needs, traffic numbers and incidents. Main group that discusses that is the "Ausschuss Unterer Luftraum" (commitee lower airspace) in which all stakeholders are represented, mainly the DFS, DAeC, VC, airlines and airports. Now, VC represents around 10.000 professional pilots in germany, DAeC represents over 30.000 glider pilots, not to mention ultralight pilots, hang glider pilots, paraglider, parachute jumpers and private pilots flying SEPs, MEP, single turbine etc, helicopters and so on. So the DAeC has quite a huge lobby group, and their representatives in that commitee often fly for major german airlines in their day job, so know both sides of the medal and are very good at counter arguing those that want more restrictive airspace layouts.
And german airlines do training programs on class E as well. It is part of the destination briefing package if there is substantial private aircraft traffic around an airport, the airspace structure is part of the route manual and should be discussed during approach briefing if one of the pilots is unfamiliar with the airport. And of course a good lookout as well as company speed restrictions are encouraged or even enforced. And of course many of the professional pilots started out as a private pilot early on, like myself who started glider flying as a teenager at age 14. Quite a few are still active private pilots and do provide valuable information to their colleagues.
Yes, airprox events do happen, however the numbers are, despite rising traffic levels, very small. Midair collisions happen even less often and mostly between private pilots close to uncontrolled fields, although the military made a few a while back until they changed their training.