The point is that unlimited supply (fiat) can buy everything and is centralized so its value is stable and declared by the government.
While bitcoin (limited supply) isn't controlled by the gov't which has its own value predicted by its supply and demand through us . I don't know if this answer will satisfy you.
But what is the point of having a money supply that is limited like btc when another unlimited money supply can buy all of that supply
Man you are just repeating your question even though I've answered it already that fiat can buy everything and about its inflation/deflation.
Your question is confuses me to be honest and I don't know what answer can satisfy your question. Could you please give your point with that question? if my answer doesn't satisfy you, let's wait if someone can explain it better until you get satisfaction.
I guess OP understands it now but if it is now enough for him, google is free all the time. Decentralized and centralized money is totally different and yet the government couldn't buy everything in the market, they don't have such power to take those bitcoins from every people around the world. Of course, the market will notice that if someone was buying but no one is selling then they would stop, right?
For easier thoughts, imagine that you are selling something which you can make it freely? What it's like? Unlimited? Nah, you're wrong you were just making it worse, everything is connected in the society because everything is a fixed data already.