It's always puzzling to me why someone will buy a game on Day 1 of its release on Early Access and believe that it will be perfect.
Do you have any idea what the difference is between internal testing / small closed beta and releasing it to a massive general public? All sorts of machines with all sorts of settings all trying to run the same game. You're going to get bugs. You're going to get performance issues. That's the point of Early Access — to get a large sample size so you can get an idea of what needs to be fixed.
As far as the controls being bad, as far as I can tell it's almost identical to Warband. It's always been somewhat clunky.
I personally spent a lot more time playing the mods than I did the base game (and probably will with Bannerlord, as well) — but the game is pretty much exactly what I thought it would be: Warband with increased visual fidelity and a nicer UI.
But by all means. Refund the game. Announce it to the world. Whatever you do, do not stick around and try to steer the game towards a better version of itself by testing it and reporting bugs and issues. That would be far too productive for someone that was evidently expecting the full-release version of the game when it was stated many times in the Blogs and the store page that there were absolutely going to be problems and content that hasn't made it in the game.
And please explain to me how this game's Early Access is a "marketing strat". This year will see the release of not one, but two of the most highly anticipated, long-running development games: Bannerlord and Cyberpunk 2077. People have been eagerly awaiting Bannerlord for 8 years. 80k+ reviews on Warband with an Overwhelmingly Positive score. This game was going to sell itself with or without marketing, because word of mouth and youtube let's plays had already spread the legend of the first game.
I've encountered some stuttering. The game absolutely hates it when you alt-tab. It appears to have a memory leak, but can't confirm. Sometimes the stuttering happens in the midst of combat and I end up getting BTFO'd because it frame-skips and makes it hard to anticipate an attack. But this is all stuff I pretty much expected.
You knew what you were buying. If you didn't know what you were buying, it's because you didn't read. Though I don't blame anyone for refunding the game if it's nearly unplayable performance-wise and waiting until things get ironed out (or they update their own computer). But for goodness sake, stop being an entitled brat.