[mytailorisrich]

No, there are no "different levels of assimilation", by definition.

Language is a basic requirement for integration, by the way, way before assimilation.

I think your last sentence misses the point that there is no obligation to accept immigrants and that the host country is sovereignly free to accept or reject anyone they wish.

[trueismywork]

Thats what OP was saying though, if countries want assimilation to that high of a degree, they should encode it in a law. Otherwise, they are being duplicitous by inviting skilled workers on one hand and then creating structures which drive them away.

For example, there can be a legal requirement to have a B2 level of German within 3 years of being in country, if the requirement is so important.

Right now, the policies say one thing and politics say another.

P.S. : the real reason such a law would never exist is because it would drive a huge amount of skilled immigration away and this is something also politicians cannot afford.