Comes down to a misrepresentation of history. Germans were never known to be efficient, they were known to be precise with everything, including bureaucracy. This happens to be handy with machinery, but not much else.
Really I think that they just landed on some really successful marketing.
It depends. For some machinery the complexity is inherent, this makes German machines very good at what they do. But this approach does not tend to scale well, which is part of the reason the German economy tends to be fairly specialized with „hidden champion“ SMEs.
Made in Germany has (had?) a very positive connotation to it, but for historic reasons.
The world got faster, but german industries and politics never got the memo.
They laid 600+km of cables wrong ultimately delaying the project by 6 years.
It's a "cover your ass" mentality that resists any changes.
Germans are thorough, not efficient.