I think you might be talking about me. I absolutely do NOT want to keep you from having the assassin you want to have. I was just responding to the survey.
Keep in mind that there are maybe two people here who have said anything like this out of your 80+ survey respondants, and I didn't even say I don't want an assassin the game. And I really didn't say that the subclass should not exist. What I don't want are mechanics for instant kills. Your particular vision of what an assassin needs to be revolves around this idea, I think, but it doesn't need to.
An assassin class strong enough to operate in a way you want it to ... effectively, to solo-kill oponents reliably enough to make the risks worthwhile ... doesn't fit into that way I want to play D&D. The assassin subclass as it exists might be weak and could use some tweaks, but I wouldn't say that I don't want it in my game. I get that it might not satisfy a lot of players, but it's not designed to operate on its own.
I mentioned before that I think an assassin class as you imagine it could work very well in a party of one or two. I'm imagining the options for spell-based assassins with stealth and subterfuge magics and a couple of potent attack spells and it seems like a lot of fun.