Peter is warning believers as highlighted in red from false teachers and saying many will follow their destructive ways as they exploit you with deceptive words.
Why would Peter warn believers of this if Peter didnt see it as an importance.
I just read through it again. It says the false teachers are the ones doomed...
"But there were also
false prophets among the people, even as there will be
false teachers among you, who will secretly bring in destructive heresies, even denying the Lord who bought them, and
bring on themselves swift destruction. And many will follow
their destructive ways, because of whom the way of truth will be blasphemed. By covetousness
they will exploit you with deceptive words; for a long time
their judgment has not been idle, and
their destruction does not slumber"
It says "their destruction". Doesn't say anything about destruction of a believer. Emphasis above is on false teachers and false prophets.
Yeah, as a believer you don't want to get sucked into false teachings, getting lost in the shuffle. As the scriptures say....
Ephesians 5:8-11: "For you were once darkness, but now you are light in the Lord. Walk as children of light (for the fruit of the Spirit is in all goodness, righteousness, and truth), finding out what is acceptable to the Lord.
And have no fellowship with the unfruitful works of darkness, but rather expose them.
How can God use you if you're following heresies. So pretty important, hence the warning to be aware of it. Nothing about losing salvation though.