I tried HS2 (The 'engine' used to make this) & all I can tell you is there's a ton of stuff to learn about it & get used to, especially when it takes up so much space in your drive & the crazy amounts of mods you'd have to get used to, to create something of this quality would be really difficult.
I'd even go so far as to say it's a miracle that the dev is still going on strong 'cause if it were me, I'd surely burnout. Might be glazing but this is why Caribdis is often regarded as the greatest when it comes to AVNs. I also admire the fact that Cari is taking their time to put out high quality. The latest version is proof of that. So it may be slow but the wait will be worth it, no point in rushing the dev.