I don't agree with the "Gen X metric", I do agree with low MTTR.

Time has changed, but back in the days there were basically 3 types of servers. Linux, Unix, Windows. The last one was the least stable and used most resources. Here we are, 20 years further, still the same systems and still Windows uses most resources. No more sudden blue screens tho

MTTR sounds more abusable. Out for 60 s? Just schedule 1000 0.1s outages to get MTTR down! You could use https://en.m.wikipedia.org/wiki/Bradford_Factor to account for that though.