There are so many False Gospels being Preached today that do not lead to Salvation. Many people think they’re Saved by: Good Works only, being “Religious”, Going to Church, getting Baptized & Confirmed, once having said the “Sinner’s Prayer” in their life— but there’s no evidence (fruit) of Genuine Salvation (i.e. just False Assurance), or because they “Feel Saved”.
Narrow Gate
Then there are those who just believe mental Facts about Jesus (I.e. head knowledge), but they have never Truly Repented-&-Believed— put their complete Faith in Jesus Christ as Lord and Savior.
Does Doctrine Really Matters?
Is it enough to "believe in Jesus" in some amorphous sense that divorces "faith" from any particular doctrine about Him, or is doctrine—and the content of our faith—really important after all?
Scripture plainly teaches that we must be sound in the faith—which is to say that doctrine does matter (1 Timothy 4:6; 2 Timothy 4:2-3; Titus 1:9; 2:1). It matters a lot.
"If anyone advocates a different doctrine, and does not agree with sound words, those of our Lord Jesus Christ, and with the doctrine conforming to godliness, he is conceited and understands nothing" (1 Timothy 6:3-4, emphasis added). That's why there are so many false preachers and false doctrines nowadays.
Sound, biblical doctrine is a necessary aspect of true wisdom and authentic faith. The attitude that scorns doctrine while elevating feelings or blind trust cannot legitimately be called faith at all, even if it masquerades as Christianity. It is actually an irrational form of unbelief.
We say out of Love
A wolf in sheep's clothing
"A person with a pleasant and friendly appearance that hides the fact that they are evil."
Cambridge Dictionary