...In essence, the device we use does not have a problem whether Android or iOS or others, the problem starts from downloading the wrong wallet
Nah, it's not as simple as you describe. Even if you download the actual official wallet and verify PGP signature and keep your mobile from installing multiple apps still you are exposed to internet, as long as the device is connected to internet you are prone to hacks in one or another way. Which is why the recommended way to store crypto assets, is cold storage it can be a device or hardware wallet but should be isolated from internet forever, the moment it connect to internet the security could be compromised.
Online wallets can also be used to store little amount of bitcoin that you would need to spend. I only have little amount of bitcoin that I do spend weekly or biweekly in my elecrtrum wallet for Android. I only store the bitcoin that I am hodling for future purpose in my cold storage because I know that I wouldn't need them anytime soon.
However, if one can't afford to buy a hardware wallet, and you have an old PC, you can use it to set up electrum cold storage. You generate your private keys offline and never connect your PC to the internet. Your wallet safety is in your own hands.