There's no hard wonder limit and you can add as many of those one wonder mods running around as you want. But total number count of wonders is a concern if you want to create a balanced game. Too many help Tall Wonder goings civs. I personally would agree that there could be a few more late game wonders than there are currently, but for the mod, it was decided not too add too many at the same time and to cut down the less popular/effective ones.
Neuschwanstein is such an example, if you want to represent German Engineering and their Golden Age 1815-1920, the Brandenburg Gate and Heidelberg University fit better. You can also find more astonishing engineering feats than Neuschwanstein (Alpine tunnels, railroads in general, some of the canals, etc. ...). But yes, I agree, Neuschwanstein is shiny and pretty to look at, its astonishing, but in the end, it's the result of a crazy person being monarch of Bavaria. It fits the "wondrous" criteria, but it still is something I like to call "Hollywood", popular history and themes and myths that maybe shouldn't be reinforced. It wasn't that big a deal
And then there comes the other side, the gameplay side.

and

on Castles helps a wide empire much more than a Tall one, but there are other wonders that are more urgent for an empire that's not going to build too many wonders anyways. It also requires you to build castles which f.e. puppet cities won't do for some time (right?) and which are not a priority in "core" cities. While walls are free for most wide empires (liberty policy), castles aren't. Also the effect isn't anything special and doesn't make us play differently, it's a run-of-the-mill one. That's why I was in favour of cutting it.
And yes, Happy New Year. (Sylvester is always the worst, because unlike at Christmas, you drink all kinds of alcohols on the same night..., but on the other hand, I'm up and able to post coherent texts

)