Cube has 3D models (MD2) and Quake like shades but it's not going much further. The walls are only made of 90° and 45° angles, maps are simply made of "cubes". Shortly, the cube engine is half way between Quake and Build Engine (Duke3D, Blood etc). That's weak for realistic architectures. (It's very funny, but I wouldn't make a realistic game with this engine

)
(useless notice) I use to love the
Tenebrae engine (based on Quake) and
Tenebrae² (based on Tenebrae plus Quake 3 Arena map support and a few other neat tricks) but unfortunately, it seems that it isn't on track anymore and I wonder if there's any net code neither. Also, it require good hardware and the game code is still this good old QC (Quake 1).
I believe WET engine is good enough. I mean... you can have a low-end engine and exploit it perfectly. The same way, you can use the latest technologies and never create anything interesting. Making games is always about cheating with hardware and software limitations, but until you're not reaching a critical point and you don't have any other choice, I think that's ok.