We you have experience in arctic environments I don't and likely never will. Thank-you for your service.
I think perhaps we are both reading too much in to the other person is saying. I certainly am not in a position to tell YOU what YOU need but at the same time you can't say that everybody NEEDS irons (which is probably me reading more into your comment than you actually meant).
Most folks are also not going to be carrying a weapon where there life depends on it either in service or say hunting game that can kill you back. In either of those scenarios, I would want backup irons. Out side of that though, optical sights have developed in ruggedness and reliability to the point that I at least, will never have to worry.
The Arctic is a pretty extreme environment that most humans are never going to have to experience. For the majority, the environment where a weapon is carried, an optical sight won't be rendered useless.
I would also argue that optical sights are superior in getting new shooters up and running with success sooner. They are easier to use so shooters can focus on the fundamentals of position, breath control, trigger squeeze without worrying about a iron sight picture focused on the front sight rather than the target. Eventually that should be learned but it is not more important than the other fundamentals in my opinion.
For what it's worth I used to hunt primarily with irons, and have taken most of game with them. Irons are nice and light so I opted for that and practiced with them. I'm in the process of teaching my kids to shoot irons now too since they have had initial success with optics.