Bitcoin for me is illegal when we judge it base from the original meaning of "LEGAL".
Legal in the dictionary means- 1) of, based on, or concerned with the law. 2) permitted by law.
So it all depends on the kind of government of which you have in your country.
As years passes by, some countries have started accepting bitcoin and making them legal.
Maybe by next decade, majority will accept bitcoin and legalized it.
Well, as much as I may want to agree with you, I may still want to argue that bitcoin have actually become legal since it's spot ETF was approved by the US securities and exchange commission, several countries where bitcoin used to be illegal because they banned it have actually started to unban it, for example, here in nigeria, bitcoin transactions used to be banned, but soon after the bitcoin spot ETF was approved, the present government have now unbanned bitcoin transactions.
So, in essence, I would say that, in a situation where the world power have made a thing legal, then it's legal, every other side powers still making that thing illegal is nothing but minority.