EU4 has also had a few of those updates. Not every update changed everything, but some did.

I don't really have a problem with that, though. These games, especially a new one like Stellaris, are also a search for the right approach to the game they want. Sometimes they realise (based on feedback most likely) that they took the wrong approach and have to make dramatic changes. Would you rather they abandoned the game and release a new game that does it right, or that they update the old one? I quite appreciate Paradox's approach. You get way more value out of the game than with most other games. And if they did that with Stellaris, that gives me hope, because the initial version of that didn't work for me.

And if you really prefer the old version, you can just continue playing that.