Well, I haven’t used it for a couple of years now because I can’t fly these days, but I’ve been through it a couple of hundred times and never had any problems either as a transit airport where it excels or as an o&d airport where it was OK. If it’s gone bad, then I’m sorry to hear that.
Suspect it has to do with my arriving and leaving for Africa, often flying via the Middle East. On the rare occasion I treat myself to a Lufthansa flight, or fly within Europe, it's been fine.
Sounds possible, I was nearly always using MUC as a connecting point from BHX to somewhere in Europe and it worked great, especially in comparison to FRA.