Evidently, as we’ll see near the end of your post 
You really would benefit from reading some of those earlier discussions. Unsurprisingly, the point you raised has also been discussed a lot. But okay, let’s talk about it again for a bit:
That’s true, they could completely prevent that with a build limit. The only tiny little problem with that is that this limit would have to be so drastically small, that most people would quit.
Why so small? Because lag is not caused by simply having many building pieces or placeables. It is caused by how you place them and use them. I won’t go into details because I’m tired of repeating the same explanations over and over again for people who just don’t want to look them up even when they’re given links.
Suffice it to say that if you want to use a building limit to make it impossible to lag the server, that building limit would have to be awfully small.
Note that all of the above holds true only if we’re talking about the simple numeric building limit that people like you and the original poster in this thread are talking about. There are alternatives, of course.
For example, Little Big Planet had something called thermometer, which was an indicator of how “full” your level was and wouldn’t allow you to build more than the console could support. If Conan Exiles implemented something similar for the state of the world on the server, then that would solve the overbuilding problem neatly.
Of course, that would be far from trivial – in fact, it would probably require huge effort – and it would also be completely unfair, because a server is shared by people and we all contribute to the performance degradation on it. So even if Conan Exiles had a “thermometer”, you would still have cases where player A builds something that “raises the temperature” by a few degrees (but not too much), then player B builds something similar, then player C does so and suddenly the newcomer player D can’t build a lot because players A, B, and C already spent most of the “budget”.
But let’s get to what I find to be the most important bit of your post:
And now it’s clear that we obviously aren’t talking about the same thing, because there ain’t no such thing as an official RP-PVP server. So here’s an idea: if you like how the limits work on private servers, go play on private servers. And if you want to discuss how official servers should work, then do us all a favor and spend more effort to read up on what has been discussed already before telling others to spend more effort on understanding you.
