You are correct and I will digress ...
I don't think there is a single engine plane that I would fly in the clouds or the dark. Admittedly some of the auto conversions are quite reliable. My Corvair conversion has given consistent performance & has been quite trustworthy. But as a Sport Pilot I'm required to always have visual contact with the surface and I'm OK with that.
I would also tend to think that EFI would almost be a necessity as the moisture in the clouds would tend to cause ice in a carburetor equipped engine. Of course using the carb heat constantly would work at lower power settings.
But I know very little about IFR flight so you'll have to "bear" with me ...
I fly single in the dark (did so last night and for one of the landings, I shut off the landing light as practice for the bulb burning out. I also fly IFR in a single on fairly regular basis. Yes, I would want a lot of proveout on my entire airplane before I start launching IFR or in the dark with it, but it is done widely and safely. Do I fly IFR in the dark? Not any more. Do I fly dark over mountains? Nope. We all have different comfort levels, and that comfort is largely a matter of staying cool while doing these things - panic and incapacity kills way more than equipment issues.
As moisture in clouds causing carb ice, please revisit the texts and physics of carb ice. The thing that causes carb ice is adequate humidity and carb venturi temperatures below freezing. The venturi drops temps a bunch - given enough moisture and temp drop, it condenses vapor water to liquid and then to solid. Liquid water will also do it, but plenty of carb ice incidents have occured in good visual conditions. Going with anecdotes again, I have flown plenty of IFR with carb equipped airplanes and have NEVER had a carb ice issue. Yeah, it has all been behind Lycomings, which have the carb bolted to the sump, so carb ice tends to be infrequent, but that is what the carb heat knob is for.
EFI does tend to eliminate carb ice because there is no carb. You can still coat the airfilter with ice and choke things, but that is what the alternate air door knob is for.
Billski