People are in this project on their spare time. Developing even a very rudimentary aircraft takes a few days and a more complete one with a cockpit and believable behaviour takes probably a couple of weeks. The more complete models are months of work.
If you really want to have those aircraft, the best way to get them done is to start doing them yourself.
Believe me, when you have demonstrated that you are willing to learn using new tools and acquire new skills you will get more help. Consider also that some of those tools and skills can be used outside FlightGear as well.
I do know that I seems daunting at first, I have been there myself (or rather, still am, to some extent*). I had wanted to, but at the same time avoided to learn Blender for years, but I learned 3D modelling basics in about 2-3 weeks and started making some cockpit instruments. I found that there are many good tutorials on YouTube.
Please, do give it a try. It can be fun to the point of being addictive at times. Also many of us would enjoy seeing you learn and develop new skills and see what you would do with those.
* Though I am more interested in improving one of the aircraft, the Mirage F1.