That's the view of Jesus' later followers, not of the man himself.
The John passage isn't especially reliable. [0]
Also, you're forgetting what Matthew and Luke both reported that Jesus said about just what's needed for salvation:
<blockquote>
25 On one occasion an expert in the law stood up to test Jesus. “Teacher,” he asked, “what must I do to inherit eternal life?”
26 “What is written in the Law?” he replied. “How do you read it?”
27 He answered, “‘Love the Lord your God with all your heart and with all your soul and with all your strength and with all your mind’; and, ‘Love your neighbor as yourself.’”
28 “You have answered correctly,” Jesus replied. “Do this and you will live.”
</blockquote>
(From Luke 10:25-37, emphasis added, footnotes omitted [1].)
[0] http://www.questioningchristian.com/2006/05/synoptic_christ.... (self-cite) Scroll down to "Problem: The Passage of Time." Tl;dr: From what's known about the author of the Fourth Gospel, his self-promoting account, decades after the facts and at odds with other accounts, simply isn't credible.
[1] https://www.biblegateway.com/passage/?search=Luke+10%3A25-37 (the parable of the Good Samaritan)