The operative word in the above statement Erik is 'could'. The fact is it wasn't. Same story with the SL and SL2, too expensive and too complex to fix and therefore not adopted by the majority of pro users.
hmm I don't think so for the M5.
M5's WERE very used by pros who much appreciated the new features compared to the M4 (TTL, shutter speeds in finder, faster film rewind, faster changing of shutter speeds etc). That is why you will find so many worn M5's in the used marketplace. In my experience I've seen a higher percentage of worn M5 cameras than worn M3, M2, or M4.
The problem with M5 sales is that the huge doctor/dentist Leica fan boy crowd was buying the less expensive CL while at the same time complaining about the size of the M5.
Stephen