And this right here is how flame wars start. You come in with an attitude, you got attitude back, and now you want to escalate it with even further attitude, It's one thing to state your opinion. But to end sentence with, "Slot well, play well or try another powerset" is just straight up asking for it. You could have just as easily made your point without the snark.
As far as your point goes, it's kind of hard for a lot of players to be willing to be okay with your point since, by time most players reach the final part of their characters, (getting them IO'ed out, Incarnates) they put that character away and start a new journey with a new character, only to break out the fully IO'ed character when called upon...unless...it is their main character and they are always playing to get the next badge.
So saying that the build is fine once somebody is fully IO'ed out, isn't really helping. Keep it cool, man. Say your point, give your opinion, you never know, somebody might just agree with you; but adding the snark at the end is pretty much going to guarantee that whoever you're giving the crass to is only going to see the crass and not your point.