I don't agree with you here. It's clearly about workflow that require hand building terrain in 3ds max. An expensive piece of software, and forgive me harsh words, but very stupid workflow.
I have had direct conversations with people who were doing terrain add-ons, and it more about the amount of work, difficulty of finding adequate meshes and reasonable textures, not to mention populating roads, railroads, buildings etc. than workflow - but perhaps I wasn't told everything.
It's a good sim, I have most of ED's sims and fly them very often, especially Black Shark. But come on, you can't call it 'open'. Swapping 3d meshes with prettier ones, or flying F-14 with Su-33 cockpit doesn't count for me.
I didn't call it open. There's always room for improvement. I think Nevada might be a hint.