Do not love the world or the things in the world. If anyone loves the world, the love of the Father is not in him. 1 John 2_15.
Here John the evangelist warns against loving the system of the world, which includes all of its politics, philosophies, sporting events and athletes, entertainment, singers, actors and the like. We are not to love the educational system which is of the world. All that the world stands for is not to be loved by those who claim to have professed loving allegiance and loyalty towards Christ.
Not only is John warning against love of the system, but he takes it one step further by warning against loving the things found in the world; riches, property, status in life, food, drink, celebration, family life, ect.. ect.. the list goes on and on, nevertheless these things and its system are not to be loved.
I (Jesus)will no longer talk much with you, for the ruler(the devil) of this world is coming, and he has nothing in Me. John 14_30.
Love for the world and the things of the world is nothing less than idolatry, it is the worship of the devil, for he is the one who has perverted the world, it is his system and his toys that he uses to keep sinners enslaved to sin and blinded from Christ. If a person knows anything or anyone better than he or she knows Christ, then it is evidence that such a one is in love with the world and the things in the world. You are either in the world or in Christ, but not both; for the two are not inclusive but rather exclusive.
The evangelist is not a legalist, telling us in order to be saved we must start loving Christ more than the world, no, not at all. But what John is saying is that if one is saved, they will begin to love Christ more and more while loving the world less and less, proving that the love of the Father is within them.
And so beware, that a wicked heart of unbelief not be found in you! Examine yourself and make sure that you are of the faith!