OXC is a lot more advanced than Doom.
Just not in all aspects.
I would just say, perhaps openxcom is younger than zdoom and all its "family", as well as perhaps, doom was made a bit more modifiable out the gate than xcom was, on release, as far as I'm aware.
On that account, I would say the entire scope of "all" developers, and "all" source ports / resources, zdoom and others are perhaps slightly more advanced, but NOT because lack of talent (talent is obviously there!) but rather, slightly smaller community (maybe?) and the fact xcom was built a bit different in the first place anyways, as far as I know, AND, that zdoom, ect, has had over twice as long in development of openxcom
Not trying to be rude to any of the developers or anything else here, but I'm just being realistic : The amount of scripting and capabilities added to some of the source ports for doom are pretty unreal, in the comparison of vanilla play, and extremely modded play, where as openxcom is making great strides, and obviously has already, but is still working on breaking many "old" restrictions of vanilla. And this, AGAIN, has nothing to do with talent, but has everything to do with doom modding / tinkering, on a large community, has a good 10 or so year start (from what a bit of research on google tells me) when you talk about zdoom, gzdoom, maping techniques, ect. So I would say doom, in all its branches of modding, is a LITTLE more advanced, but thats only because it has a few more years of actively modding under its belt.
But, I'm getting a bit off topic here... hope nobody got offended by this
I say again, talent is most certainly there, but an indifference in time applied is EXTREMELY hard to compensate for.
For the record though, I would say the fact VANILLA xcom is far more advanced ANYWAY, speaks a great deal too.