Whenever someone says they don't believe love exists they're usually referring to their (own) life experience.
One would have to be blind not to see the various happy couples holding hands, kissing, laughing, and playfully interacting with one another. In the U.S. alone over 2.3 million weddings take place each year. I suspect most of these people believe they're in love.
Needless to say there are also other various forms of love as well such as that between a mother/father and a child, friendships, siblings, and extended family. Just about everyone has someone in their life that they love or believes loves them.
There are over 7 billion people in 196 countries on this planet. Just because one has not been "in love" or felt love does not mean it doesn't exist for the rest of the world.
Each of us chooses our own friends, lovers, and spouse. Ideally with age comes wisdom and we learn to make better choices for ourselves. If you want something different you have to do something different. Not only do I believe love exists I see signs of it everywhere!