John 1:9

The true Light, which enlightens everyone, was coming into the world.
John 1:9, Modern English Version (MEV)
 
The theme of John the Baptizer being the harbinger, the herald of the coming Christ, is an important one but, as the Apostle John so meticulously points out, not because of who John the Baptizer was. As we've said on so many occasions, and will do so on many more, it's all about Jesus. John the Baptizer's purpose was to prepare the way for, and to point people to, Him, no more, no less.
 
From Albert Barnes’ Notes on the Bible:
 
That was the true Light - Not John, but the Messiah. He was not a false, uncertain, dangerous guide, but was one that was true, real, steady, and worthy of confidence. A false light is one that leads to danger or error, as a false beacon on the shores of the ocean may lead ships to quicksands or rocks; or an “ignis fatuus” to fens, and precipices, and death. A true light is one that does not deceive us, as the true beacon may guide us into port or warn us of danger. Christ does not lead astray. All false teachers do.
 
That lighteth - That enlightens. He removes darkness, error, ignorance, from the mind.
 
Every man - This is an expression denoting, in general, the whole human race - Jews and Gentiles. John preached to the Jews. Jesus came “to be a light to lighten the Gentiles,” as well as to be the “glory of the people of Israel,” Luk_2:32.
 
That cometh into the world - The phrase in the original is ambiguous. The word translated “that cometh” may either refer to the “light,” or to the word “man;” so that it may mean either “this ‘true light that cometh’ into the world enlightens all,” or “it enlightens every ‘man that cometh’ into the world.” Many critics, and, among the fathers, Cyril and Augustine, have preferred the former, and translated it, “The true light was he who, coming into the world, enlightened every man.” The principal reasons for this are:
 
1. That the Messiah is often spoken of as he that cometh into the world. See Jhn_6:14; Jhn_18:37.
 
2. He is often distinguished as “the light that cometh into the world.” Jhn_3:19; “this is the condemnation, that light is come into the world.” Jhn_12:46; “I am come a light into the world.”
 
Christ may be said to do what is accomplished by his command or appointment. This passage means, therefore, that by his own personal ministry, and by his Spirit and apostles, light or teaching is afforded to all. It does not mean that every individual of the human family is enlightened with the knowledge “of the gospel,” for this never yet has been; but it means:
 
1. That this light is not confined to the “Jews,” but is extended to all - Jews and Gentiles.
 
2. That it is provided for all and offered to all.
 
3. It is not affirmed that at the time that John wrote all “were actually enlightened,” but the word “lighteth” has the form of the “future.” “This is that light so long expected and predicted, which as the result of its coming into the world, will ultimately enlighten all nations.”