There's enough there (for me) to not be mad at it.

we're spoiled with the amount of backstory available through so many forms of media, it will eventually get touched upon like so many vague things in the OT did.

The dialogue from the prequels was there, palpatine hooked up to some kind of machinery was there, him not being at his strongest until receive other life force was there, that's enough for me.

Would I like more? Sure. We'll get it, just like we got more things expanded upon from the OT. Granted, this one topic is pretty big compared to the mention of things like Clone Wars, Kessel Run etc so I understand people expecting more explanation from something so bis as Palapatines return, but I'm just not mad it.