No open worlds with Unity?

I understand that it is a question already discussed many many.
I was wondering if to date (Unity 2019.3) the problem of "hiccups" in asynchronous loading has been solved.
Effectively, this excludes the construction of open worlds in Unity and make almost no use asynchronous loading. The problem occurs not only in the editor but also in the build.
Has anyone found a technique that works? We know that the problem is the activation of the loaded scene.
There are many tutorials that explain the asynchronous loading of the scenes, but the examples are all with almost empty scenes and therefore very light to activate. If you try with soils with many objects, the slowdown becomes of the order of seconds ...