Decentralization doesn't inherently guarantee freedom; it's a nuanced concept. While Bitcoin offers decentralization, control over mining power and major exchanges can still influence its direction.
That's not true. There is a difference between manipulation and control because a lot of times, one can manipulate something without having control of it. While it's true that if an individual or an entity manages to gain access to over 51% of the total mining power, they can manipulate blocks, do double spends, etc., that doesn't give them control of the network or the price but it will eventually destroy everything if they keep misusing their powers. So I don't call that control because it isn't controlling if you aren't able to use the powers you have acquired.
Talking about exchanges, they don't have any power to direct the price or the network no matter how many coins they have under their hands. Having a large amount of Bitcoins might make you able to manipulate the price a little bit by creating buying and selling walls in the market but that doesn't give you complete control.
The decentralization of Bitcoin is mainly about it not being managed by a single entity which is true and will always be.