I really have no interest in continuing this discussion... people who work on the M70 know why it has the reputation it does. And there are tons of people who work on the M70 since so many of them break. Theres a reason these V12 paperweights are littering junkyards nowadays...
S38 and S14 yes had timing chain guide failures. But an owner of these engines should replace these preemptively - thats part of "maintenance" - when I say "well maintained" that includea preventative maintenance to prevent well-known problems.
S54 had rod bearing issues early in production but later models, keep up with valve adjustment and the S54 is pretty bulletproof. They have a few odd problems like the cam hub but there are a LOT of S54s on the road and very few have major problems with things like that
S62 is an extremely reliable engine, and my favorite BMW V8. With proper maintenance, these engines can last forever. I would even say they were more reliable than their M62 bretheren who had timing chain guide failures. Carbon build up should not kill an engine, the S62 needs to be revved hard to "blow out" the carbon. Babying an S62 kills it. Driving an S62 hard is maintenance for it
VANOS is a more major problem for the S62 but it wont fail catastrophically, just sound like a diesel
M60 had its quirk's but BMW fixed it with the M62... BMW was still learning how to make its products work in all markets at this time
M70 had electic problems, fuel delivery problems, throttle bodies, crankshaft sensor... I could go on and on. The M70 is the modern BMW engine I have the least hours working on but also has the MOST problems associated with it of any BMW engine I have worked on.
The M70 engine block itself may be bulletproof, but EVERYTHING bolted to that engine to make it spin is a ticking time bomb.
Continue to debate if you want but I am speaking from personal experience not just conjecture and at this point any further discussion will just become "no, you" "no, YOU" kind of stuff.
Cheers