Why is the F-22 not a stealth plane and nowhere near as invincible as in real life? Because the in-game unit could easily be a modified production model that got rid of many expensive features in order to make it economically viable in the first place. It's also a lot rarer, as only General Griffon even has access to the F-22 Raptor, whereas Bradley and Thorn use the F-35 "Widowmaker" instead.
The European Union prior to the GLA attacks was very much on the verge of imploding on itself even as its leaders tried remolding it into an United Europe. Even had the aforementioned terrorist fiasco never taken place, it wouldn't take much to take down the EU altogether. If anything, the attacks both accelerated the process and provided the necessary justification for the mass Velvet Revolution that would result in the ECA.
While it makes sense that the GLA may lack female members (aside from the Angry Mob if you look closely since these are civilians taking up arms), one may be just as curious as to why the ECA seems to have more female voices and units compared to everyone else. This could be chalked up to a number of European countries having significant gender equality in real life. Amusingly, the only frontline infantry in the whole mod that is female and has a gun is the ECA Medic.
On the other hand there are no female Generals to play, but this is mainly because there were none in the original version of the game either which was supposed to have 3 playable Generals per faction from the get go and the mod team's aim is to build up on that (official Doylist explanation: getting pictures of female 5-star Generals that can be used for the mod is almost impossible, so the team had to make do with male ones). Female generals exist though since the ones from ZH are still canon.
Why does China use out-dated FLAK shells instead of more modern missiles? Because all their ECM, EMP and what-not technologies are designed to interfere with missiles, so they try to prevent hurting themselves by barely using any missiles at all.