Chances are you are not.
Sometimes it can be difficult finding someone who is as interested in genealogy or family history as you are. Sometimes relatives have an interest, but more of an interest in some of what you find and big discoveries that you have made. It can be more difficult to find someone as interested as you are in transcribing barely legible documents, reading through page after page of unindexed records, etc.
But they may be out there. They just not may be as closely related to you as you wish. They may also not be one who actively seeks out other family members with whom to share or exchange information. While that may seem strange, they also may have gotten tired not finding relatives who aren’t “quite as interested as they are” and have stopped reaching out. It does happen.
Recently while looking through my AncestryDNA results, I came upon a tree compiled by a relative–a descendant of my 4th great-grandparents. A very complete tree with information that was sourced and consistent with what I already had. Years ago I made contact with a descendant of a set of 5th great-grandparents who is very diligent in their research. I’ve also seen trees that were extremely less complete and less accurate.
Not every relative you find will be as “into” research as you are. Some may be more “into it” than you (yes, those people do exist). That’s fine. Focus on those who seem to be in the same place as you are or seem willing to communicate and share information. Don’t burn you bridges with others who are in a slightly different research place. Those relatives may have family ephemera or information that you do not. They may also develop later research interests that more closely match you own. You’ll quickly get a feel for if they want to discuss research as deeply as you do.
And you can’t communicate constantly with every relative you have anyway. It’s simply too overwhelming.
But while it may feel like you are the only descendant of your 4th great-grandparents on the planet, you probably are not. Probably–there are exceptions.