I think it is only illegal if there is a law that makes unregulated market illegal. The crypto market in my country is still largely unregulated but the people are free to use and trade any cryptocurrency from both local and international exchanges. Some countries have already imposed their own regulation to curbe some illegal activities and protect their people financially.
It seems like what you have told a lot has happened to the developing world, there are still many who have not received developments about crypto so it is too late to make regulations that can regulate it. but indeed, if there is no regulation, this is clearly illegal. because crypto users need definite protection, so that it doesn't become chaotic in the future.