Well Mark, with the slightest wink to hyperbole I would agree with most of your assesmsnt.
However, after two test drives you and I diverge on the 991;
First, would challenge that you took a 991 to its "limits" on a test drive. If you did, I'm happy that I wasn't anywhere near. I find this especially difficult to swallow considering your last sentence...
Second, I'm confused as to: "...The attention to detail is the best of any car I've owned...". What did you mean? Honestly, I'm not sure of the context. Could you expand?
Finally, let's get serious. Every gen from now on of every car commonly available will be dictated first by bean counters. A prime example is the new 991. Do you think, for a NY minute, that that car is actually more expensive to produce than say, a 993 in today's dollars (Euros)? Do you think the interior (shamelessly derived from a Panamera and Cayenne) is more, or less expensive than previous designs. Cross-platform parts are just that, and decease costs considerably.
The 991 is a very competent car. NOT a supercar. No way, no how.
Sadly, the new M3 shall be the same, no doubt.
Yes, it may be faster, and the ringers may take it around the 'Ring faster (which would be important if I drove the 'Ring... fast) but I'm sure things will be lost too.