Um, first of all, it was a 1984 BMW 325e... welcome to not everyone has a brand new cars (there is no way in hell I could even afford a new BMW). So, yeah, it's a lot less complicated than a 2014 BMW (30 years older). It's simpler than your 90's car you are saying I can't compare it to with how easy they are to repair cause they are simpler. Also, do you have so little faith in BMW that you think a newer car by them would already have so many issues that some guy trying to work on it was fed up with it?
And yes, I trust his assessment on these things. He's very smart, he has definitely shown he is very competent. I've known him for 15+ years and I've seen the stuff he does and he does very good work/design work. When he does something, he does it well. He's built his own little chip for one of his cars to increase performance and he knows a lot about electronic stuff (he at one point said he should have gone into EE because there's more selection of jobs. Granted, I am obviously not an engineer but I'm smart enough to at least understand his explanations of stuff when he does the "explain it like I'm 5" (He doesn't mind explaining stuff to me either. My problem is I can understand it but I tend to just remember the generalities and not specifics so ask me to explain later and I'll be able to say that what I can remember is the end result and the explanation made sense so I trust the end result is right but I can't tell you the explanation why cause I forgot). I can tell you the air venting on it constantly broke because it had a very complicated system of doing it that my BF pointed out there was a lot simpler system that would have worked just as well (and the more complication you bring in the more things can break). The electronics on it were sh** (hell, even BMW fanatics told me the reason 3 series keep their value better than 5 or 7 series was because less electronics on it to break). By the time we sold that car the windshield wipers would variably work, I think the only thing on the dashboard that worked was the tachometer and we tried replacing the dash several times and it took three or four tries to find a dashboard that didn't have the instruments broken. The first year we had the car it had some obscure electrical issue that would randomly show up and then disappear. I'm amazed he managed to find it finally (it caused the car to randomly stall on me for a bit and then it would work for a few months before doing it again). Apparently the way they put in the clutch/transmission system was done in a way to require a special part to reach certain parts (he ended up making his own tool to get to it) but could have easily been designed differently and worked just as well and been easier to work on that stuff. And some electronic chip he showed me had the prongs that connected really long (he said longer than any other car does). ANd I can understand that the more length you put on something the easier it is to break (more leverage for something to put pressure on it). And it broke.
Oh, and he designs those planes you fly on so you better hope he's better than a BMW engineer
.