The problem is that if those limitations applied to CNs, then the overlord nation that created them in the first place would get basically no income from them. The overlord needs to get about what they'd get if they'd colonized somewhere else in the world, otherwise there is no reason to colonize.
So either the income from colonial vassals system needs to be changed such that they get ~50% of all the income their CN makes, or the CN needs to be able to go under 50% autonomy.
The unfortunate conclusion of your defense here is that the strong nations can't be nerfed because it would make them too weak, but the weaker, less viable nations need to be nerfed because otherwise it's possible for them to become strong.
That's not a sound basis.
You're being disingenuous (also, outperforming Spain's real-life empire is actually pretty tricky). It is risk-free and opposition-free to do so with any nation with easy access to same-continent colonisation; that isn't true of most other countries.
As if human colonial powers don't have it risk free and opposition free to create CNs. If you assert that to be the case for natives, it's even more true for the nations that can actually create CNs and fight others on equal footing right away.
Also, it's somewhat disingenuous to cite Spain's IRL performance, which depended on events that are quite lucky in-game in terms of European holdings, and wide spread disease + timing in the new world.
In the meantime while I am sure there are people here who are honestly complaining about this change to be I feel like a lot just wanted to complain about something and jumped on this.
Changes like this stick out sorely because they can't be rationally defended, evidenced quite profoundly here. A majority percentage of patch changes can be rationally defended in their current implementation. Much of the frustration, patch to patch, comes with the developers leaving in features with nonsense defense or no defense against protest of the community that said changes don't make sense for either gameplay or historical reasons (or in the worst cases, such as the truce timer, both).
Here, we have an example of one western nation receiving full potential benefit from colonization, despite being foreign to the land, while other western nations still can't ever get more than 50% utility out of it. The benefactors of the 1.7 and before full benefit are none other than the strongest western colonizing superpowers in the game, while other nations eat a nerf. Since even the developers don't have a leg to stand on when it comes to debating why colonial nations are inherently superior at administering native land than a westernized native who spent its entire existence adjacent to the same land, they instead fall back on "the ROI for weak nations was too good, even though they were still weak nations".
That rings hollow, and as typical this kind of change comes to light just before the game launch. Since people can't actually debate against this, they don't. They use logical fallacies instead. I'd love to be shown wrong there though so we can have a real debate as to why it is that weaker nations needed to be made relatively weaker.