I don’t “think” it’s impossible to track, I know it is (but only with proper measures). If you buy small amounts of crypto with an exchange, “wash” them (Helix is an excellent service with only 1% fee) properly to another wallet not linked to your ID (there are many of these), so it’s impossible to track because there are so many addresses to crack, speaking in absolutes it’s not “impossible” to track, but it is so difficult that, at the state of the art, it may require months for a single transaction, and you have to count “mixed” coins as a cluster of transactions. I hope I’ve been clear. Obviously the use of a VPN and constant changing of the receiving address are mandatory measures.