I kind of feel like the Royal line has been nothing but manipulated. Usurpations, rule changes, and exceptions to primogeniture have been there since the beginning.

It'd be nice if this led to just getting rid of the concept of royal families in general

The line has been manipulated several times by Parliament, including the selection and elimination of kings.

The point of the royal family now isn't to be a defined lineage, but an agreed upon vessel to hold power when Parliament temporarily breaks. Even then, Queen Elizabeth II was kind of shit at it.

I’m not sure what the point is in any case. Whatever about how the monarch is chosen…having a monarch is bad! And this monarchy is particularly bad!

A monarchy is a family business. Anyone in the family can run it. Monarchies are inherently unstable when the monarchs die because of this.

Seems a little threadbare as a theory.

People have been adding other people to royal families for the entirety of recorded history.

Sometimes its through marriage, but sometimes its adoption, sometimes they just make up a lineage.

Now, theres arguments against royalty, for sure, but if the royal family wasn't allowed to prune itself, find the best people and merge them into the royal family, etc, there never would've been royals in the first place. Royal families begin with individuals but they remain by caring about "good breeding" (and other ways of consolidating power).

Consolidating is the real purpose. It can be obscured with religious lines of divinity, or what have you, but royal families are always shopping for people to incorporate.