To offer a more serious reply:
I was personally drawn to non-denominationalism when I left Pentecostalism. For the most part, the draw was for ecclesiological reasons. There was the sense of denominations causing division, and non-denominationalism was seen as an antidote to that. In a naive way, I, and many non-denominational Christians, believed that removing explicit labelling would lend itself to greater unity.
The problem with most, if not all, of non-denominational Christianity is that they are non-denominational either because:
- They’ve got fringe beliefs very few people would be willing to accept. One church I saw had a ton of race-based beliefs that one would have to accept.
- They’re Baptists or Pentecostals who, again, want to get rid of labelling. Very frequently, they also don’t know a whole lot about all the different ways Protestants are divided and often think things like the paedobaptist and credobaptist debate is a purely Protestant vs. Catholic one.
Personally, I was in the second category, and almost all non-denominational Christians I’ve met are too. The problem, beyond just the fact that they’ll probably clash heavily with the first category, is that they haven’t considered a lot of the other ways there might be a lot of internal strife such as:
- Baptism: Lutheran, Reformed, and Anglican Protestants all believe in baptizing infants, preferably by an ordained minister. Baptist, Nazarene, and Pentecostals would all disagree. Tearing down denominations won’t suddenly fix this problem, and will really come to a head as the former group start having babies.
- Church Oversight: There are multiple forms of church government in Protestantism ranging from episcopalian to presbyterian to congregationalist. Non-denominationalism, by its nature, tries to avoid at least the first two. How do you reconcile this without devolving into denominationalism?
- Authority: Traditional Protestants still hold some degree of respect for tradition and church authority. Many Evangelical Protestants are incredibly skeptical of either and would refuse to allow the recitation and citing of traditional texts. This will at least cause division in liturgical and preaching matters.
Those are just three obvious ways division will still happen, especially as beliefs are put into practice, but I could list many, many more. Again, non-denominationalism, assuming it comes more from ecclesiological concerns and not simple pride, is naive at best. Personally, once I started delving deeper into Reformed beliefs, which frequently contrasted with my Pentecostal upbringing, I realized that non-denominationalism, even when considering just Protestantism, was completely untenable unless everyone collectively decided on a standard, as denominations do, or watered down belief and practice to the point that you no longer even have a religion.