I actually have a 2004 Z4 which I love. Great engine. But the newer models with all the tech, there seems to be a lot that goes wrong with them. I think this is when BMW changed the engines beginning in 2008 or so. I still love them though, but Audi has grown on me a lot.
BMW's do have a lot of issues, but I don't think they're engine related. It's more the surrounding tech. To be fair to BMW though, Mercedes and Audi have had more issues in recent years too. It makes sense I guess, the more you build into a car, the more that can go wrong.
I ride an Alfa myself and interestingly for the Giulia and the Stelvio few users have had issues. Alfa Romeo see this as a win of course, but part of me believes it's mostly because the infotainment and the luxury of the interior is a step down from Mercedes and Audi. It's more of a driver's car.
Btw I've always thought BMW's were hideous from the front, but with the electric models I find them to be particularly bad.