It depends on what you mean by serious. If serious means making their M (for mobile) system into something tor folks who carry around a steamer trunk full of lenses, then I agree. If serious means selling a lot of cameras to folks who want to take a really good camera along that is small enough to carry most anywhere, then, I would say they are quite serious. Most people only carry one lens when traveling and at the most two (a zoom and something fast). For me, that would be the 18-150 and either the 22 or 32. I might well eschew the prime (or take the tiny 22)and take the 11-22 instead because it is such a great lens and so often useful. BTW, I have almost all the M lenses and do use them when nearby. Also have the Viltrox speed booster and note that it works quite well with both the nifty 50 and the 40mm pancake and those are both very portable combinations.
Seems like we're of the same opinion. The post you quoted was in response to the opinion that Canon should do more with the M lens selection, and in so doing would signify that they were "serious" - I don't believe that is their intentions at all. The M line of products serves a very specific purpose which you effectively stated...being mobile.
There will be compromises for a system that is focused on maintaining portability as one of it's primary selling points. If someone is looking for 2.8 zooms and fast long primes than you might as well adapt an EF lens because a hypothetical M equivalent would be heavy and unbalanced anyway.
I'm looking forward to owning an M, I've gotten enough of an opportunity to tinker around with them that I think it'll be a great addition. Hopefully I'll find a nice deal on one here soon with all the holiday sales coming up.