To be honest , I’ve not spent time analysing the issue, but feel for the people who still experience it.I've had my 2018 MBP since it came out (ordered to replace my 2012 15 inch MBP which had its fans on pretty much continuously) and, knock on wood, I haven't had any crashes. It is a 32GB RAM machine with the 6 core i9 (MacBookPro15,1).
I do use it in clamshell mode 95% of the time with a 2004 30 inch Apple Cinema and a CalDigit hub. It is used a lot - X Code, and a lot of stuff running continuously in the background, so it does get a workout.
I wonder if there is a pattern to machines that have crashes.
As far as microphone, I have an external USB one that works fine. I actually prefer it because it is higher quality if I need to use it (once per year it seems0.
And it will not be the machines themselves , but people’s individual user scenarios. So sadly returning a machine is not the answer - that is the one thing that upsets me about apple, they go out of their way to be green, as seen today, and yet still replace people’s machies knowing that is not the answer, but an interim to please the customer .