Global CSS from Neos is actually not much of a problem. The problem is global CSS leaking into Neos, which using inline styles solves to some degree but doesn’t eliminate since all inherit styles still apply. The only way to getting rid of this problem is by using an iframe for the website. Also the real problem is updating CSS/JS on page reload and media queries, both solved by an iframe approach.
I don’t see great benefit from this to be honest. One of the reasons of doing this is to make use of native only API and performance. However neither are a big problem for Neos. Good performance can be achieved with just web and if you want a actual app, Cordova can do the trick. Keep in mind that even Facebook has to rewrite 30% of their react native code to build an app cross platform AFAIR. The great benefit of building web apps is that they don’t need to be downloaded and installed. You’d have to have very good arguments having to force that on your users and for Neos I simply don’t see them. Why haven’t anyone created any app icons for saving to homescreen? Same goes for packaging Neos in an Electron app e.g.
Like mentioned in RFC: JS Refactoring Process of Backend - #43 by dfeyer, this is not exclusive to using React and can be achieved with Ember 2 as well.
This is something I find a little odd being mentioned so often. Neos is a like a program and people would be okay waiting for it to load initially. Especially if we made the waiting experience better. The difference between Ember and React in this case is minimal and matters when you have a website that people don’t load often and don’t have clear intentions/needs of using. Thus this argument is completely void in my opinion.