OXC is not a simple "rebuild" of the game to make it work natively on modern systems. It is a complete rewrite, from scratch. And definately, not a "remake".
While the devs do try to closely follow the original game, there are some minor differences from the original - simply because while some details of the game are known (like the damage formulas), some were implemented without having access to the inner working of the original engine (like the A.I.).
However, the CORE of the game is as close as possible to the original, with only minor (and "modern) improvements - like the mousewheel Warboy mentioned.
Every other option is ... well... OPTIONAL. It's simply something that you don't have to use if you don't want to (sorry Warboy for kinda duplicating your post).
You can't really blame the developers for implementing stuff like MOD support and various gameplay related options (including patching the game data on the fly to fix some of the original bugs!)
Yes, this is not the original game. If you want the original, play the original. Use the extender to fix some of the bugs and play it.
Or better yet, play OXC without any extra options activated. And while at it, report bugs and help fix them. Give a hand coding if you are able.
But whining that OXC had a different interface, different sounds and music (where did those come from?) without even taking the time to thank the dev team for their efforts and free time invested in this, is plain (and simply) wrong.
Look, I am a TFTD fan. I don't like UFO that much (though I finished it several times). Can't wait to play TFTD on this modern engine.
What should be my options:
#1 Whine that after so much time and active development, TFTD support is still not in the engine (hell, not even v1.0 of the engine is released) and be mad at the devs
#2 Help iron out bugs, give suggestions and formulate opinions on various features, to help the devs to get OXC support TFTD
#3 Shut the hell up and go do/play something else.
I'll take #2 any time.
And I'll take a #2 on anyone who whines about anything without attempting at least to give a hand in fixing it.