Just in the 9.5 category there are over 1000 listings. And many (most) from earlier versions also work just fine, so perhaps 8-9000 models, color schemes and variants. Even if you could download everything all at once, you would have to then import each one individually into Real Flight. If the directory system in RF could even handle a large fraction of those models, you'd be seeing all sorts of performance issues as it tries to display the final listings. And while there are many, many great models out there, there are a number not worth the effort. And let's not even think about the ones that are only color scheme variations that someone thought would be cool to make 20 versions of.....
You don't want, or need, all. Truely. Just pick the ones that look interesting, from time to time, and only keep what you like.