Don't forget recyclers, nuclear power, solar power, wind power. There also is a lack of building materials, such as bricks, and lamps, as well as a lack of plant options, as it's only vanilla plants now. That's a good half of the things tekkit used to provide an experience for, and now there is of course some really good mods, but it feels like there isn't much else to do, after a certain point. There is no actual tech tree, and there isn't tiers of energy either. All of this combined makes for a very boring mod pack.
So, IC2 and redpower are old and clunky, and are no longer going to be updated. That's all fine and dandy, but what happened here was the baby was thrown out with the bath water. Thermal expansion is a great mod, but it's a mod for one tier of tech. Something needs to be done about this, or it's just not going to take off.