Level-headed post even if I may disagree with you on Armstrong. If people wanna criticize certain moves he has made, that is perfectly fine. If people wanna claim that he's a bad general manager overall, then it's a bit hard for me to take that seriously. I listen to so many podcasts with former and current players, media types and other hockey people and pretty much everyone speaks very highly of Armstrong. There is nothing a fan can say to persuade me that all of those people are wrong in their assessment.
No GM has a 100% success rate with signings and trades. What I do know is that since 2010 the Blues have the 5th best record in the NHL, have made the playoffs in all but 3 seasons (only 4 teams have more appearances in that time span) and he had a huge part in building the team that brought us our first ever championship. It would take a LOT of horrible mistakes to come close to canceling all of that out in my eyes, though I understand why fans are frustrated right now. As a fan, I am far more grateful for the good things he has done during his tenure than angry about the handful of mistakes he may have made. But that's just me.