I wouldn't say that Android phones are more secure than PC or iPhone but their security has nothing to do with allowing or rejecting cookies. Crypto wallets get hijacked by infected apps that user installs on it's phone or by a SIM swap. I never heard of anyone loosing their crypto because he allowed cookies on his phone.
No common OS people are using that hackers will not look for ways to create a malware to attack the users, even the OS that are not common can still have its own malware, but hackers prefer what is mostly used by people. You are right because as Android is very commonly used among people, there are many apps on play store that are for hackers and scammers generally, there has been many people that have complained about how they funds were stolen due to fake apps. We need to knows ways to protect our devices is the best, not that one is secure than another unless it is not commonly used like the recommended Linux.