system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is SMS based Two Factor Authentication considered insecure?
gpt
The attacker could take over the phone number by fooling the cell company into thinking you changed phones.  

So then, since SMS has no authentication built in, the SMS message just goes to the attacker's phone.

An application for 2FA won't just work on the attacker's phone.  They would have to go through the process of setting up the new phone with the 2FA software, which hopefully, they can't do because they aren't you.