Why would you say this? As noted above, CASUCs were the closest to real reactors we've had in this game
Yes, they were, but Nuclear Reactors received an overhaul because people were not using them as they were intended to be used; they were meant to be something that you would actually have to plan out (hence the Reactor Planner) and keep an eye on if you wanted any high power generation, instead people got 2000+ EU/t out of 1 reactor using the exact same design as everyone else. CASUCs (CAMUCS?) do still technically exist in the way of the lapiz and redstone cooling mechanisms, and with UU-Matter in core IC2 (Not talking GregTech here, that changes a whole lot of things pertinent to this discussion), it is possible to make a major profit from Uranium cells in excess of what the old CASUCS could do, but with a lot more engineering and danger involved.