Not to be confrontational here, but: can anyone who actually knows what they are talking about list the real deficiencies of this engine compared to other more recently developed engines that could conceivably be used to develop such games?
If anyone can, great, we will all learn a thing or two. If you cannot, then why are you even saying "the engine is problematic?" What specifically is it about the engine that is "problematic?"
I do not yet have the expertise to be sure of this, so correct me if I'm wrong, but . . . many if not MOST of the OS (not the one Oracle gives away, Linux or whatever . . . but most of the actually commercially successful ones) in existence today are built on very old architectures. While all of them have been modified in myriad ways to take advantage of changes in hardware and software, most of therm are hardly "new" at least in the sense that they are evolved versions of their originals.
If someone really does know what they are talking about, please do correct me here, but . . . my understanding is that for complex software like an OS or a game engine, building on last years model is almost ALWAYS the better option than trying to switch to a completely new design that has little or no lineal relationship with the old system.