I had a similar problem when lauching DCS some week ago - I took very long (about 5 min.!) just to get the main menu. And it was porked, sluggish and
I don't want to mention how long it took to load a simple (nearly empty) mission, which ended in a slide show, although I did not change any settings at
all.
Now, although I'm not a friend of reinstalling games just because it doesn't seem to work as it should (or already did), this time I did - with anger - but
I did. I deleted the whole crap, everything! And now everything is running just fine on my humble system.
Maybe you should do the same - get rid of your current installation and download the whole thing again (stable version).
Cheerio