Okay, who's going to admit it. It's the role playing aspect. I know that nobody wants to tarnish their good, groggish name with a phrase like "role playing", but come on, admit it, you know you want it

. Well, at least I do.
I could do without minute attention to historical accuracy (Fokker DVIIs in 1917 is NOT minute, that's enormous) although the closer the better. If it is not perfect, it has to be about right. But then there is the fantasy "you are there" element. You need squadron mates that are interesting for that. You need opponents who are interesting. Sounds like ROF has neither at this point. In truth, I thought that IL2 lacked that too (squadron mates just got hacked too fast).
One of the keys to the next level of sim will be to give AI a survival instinct. If damaged, get out of the fight. If outnumbered, run. Without this, all of the physical fidelity is meaningless in an SP game. Your enemies will stupidly fight to the last, meaning a bloated score for you. Your mates will stupidly fight to the last, meaning a revolving door that moves faster than even the real WWI turnover (which was quite fast enough).
So, no real squadron mates, no historical fidelity, ... yet. Here's hoping for the best. Unfortunately, unless you are happy with canned campaigns, it is going to take code to fix these sorts of shortcomings.
Oh well, I bought mine. Hasn't arrived yet. Wouldn't have plunked down the money if the whole thing seemed hopeless. If the folks in Russia allow the community to do what they are able to do (expand the aircraft base) while the coders remain committed to improving the guts of the game and integrating community enhancements it can all work out.