Oof, yeah. We're playing an adventure path and it's getting very frustrating for some players. In ship combat, I'm usually happy enough running engineering and repairing shields, boosting power, etc. One of the other guys does pilot and is having a very unsatisfactory time. Because all of my skill checks are static (beat a 25? Easy!) and all of his are contested against the NPC pilots and, despite having basically max bonuses in piloting, it's still a coin toss every round if his maneuvers will be effective. So it never feels like he's some heroic space ace in any way because everyone else is just as good, relegating him to the role of common schmuck.
I would suggest that, if you don't have any good tips for converting 5e to a WW2 scenario, you just don't answer the question. The person is asking for tips about that, not about other systems and most people are aware that other games exist. They just have their own reasons for wanting to do what they're doing and receive assistance with that, not be told that they're wrong for wanting to do that. If no one answers their requests for help, maybe it'll sink in that they're doing something that doesn't work well. If you DO have something to add to what they asked, you can try to slide something else in, like "Assuming you're against trying a new system (WW2RPG is great for beginners), I'd start by going through the ranger's options and..." Spoonful of honey and all that.
No one wants to ask for laptop suggestions and be told "Just buy a desktop" or side-by-side refrigerator suggestions and be told to just get a top/bottom, etc. Going into it (however good intentioned) by implying their question is dumb and bad and you're going to reframe it for them is always going to put people off. And possibly, as noted in this thread, make people view other RPGs with a sour taste as well.