I will share with you my opinioin, but it will be an unpopulaire opinion. No problem, I take responsibility for it. So... In my opinion does not exist an optimal immigration policy which is valid for all countries. In this way to most countries have their own and unique immigration policy it is good, but not enough. About a standardizes process: I think the most useful it would be, if an international organization about immigration to maximize the number of immigrants for each country, based on their population, and this proportion to be maximum 5%. In my humble opinion, if more than 5% of a country's population are immigrants, national policy does not work properly. I'm definitely convienced, that actual barriers to immigration are extremely lows.

So...my opinion in subsections:

You all can see (hopefully no one of you has experienced it physically) what happening right now in the most European countries...I don't like this, and I'm sad that this can happen. I'm not racist, I never judged based on sex, religion, skin color, sexual orientation, etc...but what is a lot is a lot...

But to not talk just about negativity, and bad things... we can see the case of Germany from 1970's years... The Türkish immigrants were much more than 5% of the population if Germany...and all worked well...indeed what's more...they provided a lot of help in the recovery of the German economy.