Whether it's and advantage or not depends on your perspective. If you want the fediverse to supplant Big Tech, then no, having a culture which is not welcoming of outsiders is not an advantantage.

However, if you happen to be a part of Lemmy's "in-group", you probably don't want a bunch of "normies" flooding in and cluttering up your feed with what you consider to be low effort shitposts, or starting drama in the comments. In that sense, maintaining a barrier to entry is an advantage because, in this mindset, if they can't be bothered to wrap their head around a slightly more complex signup than usual, than they weren't going to be good members of this community.

Perhaps some will disagree with my interpretation of the two popes (I meant poles, but I'm keeping the typo) of users here. To be clear, I'm not ascribing a value judgment to either position. I think both have valid points, and, frankly, I'm not sure where I come down on it.