Everyone is entitled to their opinions and no criticism intended but I see it differently.
Sins was "done". They successfully released the original game and two expansions, added some balance changes and fixes throughout, maintained a gamesever, support and forums but were moving on to other things with maybe one day...in the future...just a hope for a Sins II. They repeatedly said no 64 bit, this is it.
Then Impulse gets sold and Brad comes out and says he didn't like the direction of his company overall and wanted to steer Stardock back to it's first love, games.
Players who kept working on things like TSOP, the normal rabid fanboy posters who loved the game and some of the pro-players who remained ardent were sitting there and I think Stardock noticed that Sins might not really be "done".
They took a shot and pulled on the fanboy base and decided to give the wheel a spin...but they also were angling to get back into the new game business.
So they made a hybrid. Half for the loyal fans that made them a success and the other half a "new game" for players who had never played or heard of Sins.
They could just as easily started on a shooter game or anything else and started fresh.
This is all "IMO" but I think Rebellion was a thank you to old players as much as it was a chance to see if they could offer a reworked Sins to a new player base.
I think the Steam numbers and sales have shown that wasn't a bad idea at all.
If you had never played or heard of Sins, picked up Rebellion--and were the sort of player that loves this sort of game--you wouldn't think, "What a rip off!"...you'd think, "Wow! Not bad!".
Sure, the caveat is the 32 bit limitation in today's dual graphics environment--but that isn't and never has been what Sins was directed at. It was made for thinking players who wanted substance over style.
Rebellion flips old strategies over and introduces new ones, took and aging engine and made itr shine again and fixed a slew of old bugs and limits that had never quite been taken care off.
It's a fair deal in my view. Old players are paying only $30 for the "new game" and that's moved towards "bargain bin" pricing. For a new player who's never run into it before, Rebellion is an absolute gem and a good deal for $40.