You can't tax every crypto trader and holders. How do you tax people trading defi on decentralized exchanges and selling on P2P using escrow. It will really be difficult. Currently, my bank doesn't know the source of my credit, it's not tied to commodity. Censoring crypto is very complex.
For now they can’t, and they will focus more on centralized platform to know every single person who are into cryprocurrency and that’s where taxation begins. Sooner or later they will require everyone to report crypto profits, this could be more good than to ban cryptocurrency at all, we will deal with this soon.
People of Indonesia still have a choice to use other platform if they really don't want to pay the tax and they still have time to transfer their funds on any platform that is out of control of their government, decentralized one or a hard wallet is a safe place for them. I remember Indonesia banning cryptocurrency before, and now they will impose a tax on it instead, this is not a new scenario anymore and good luck to their government on collecting taxes, this can be one of the hardest thing to collect.