Not too coincidentally, the author of Objective-Smalltalk, who said above that he wants to leverage Cappuccino, has also written up his criticism of React here: https://blog.metaobject.com/2018/12/uis-are-not-pure-functio...
Related: I've talked to a Cappuccino founder recently too, and my casual observation (which he agreed with) was that had they done Cappuccino all over again, they should have probably dropped Objective-J. Imo it's just a bit too much of a language bikeshedding and I don't think it would have changed framework _that_ much (proof: Swift works well with UIKit and AppKit). Though my opinion was just based on practicality of adoption; if Objective-smalltalk wants to take its time exploring around more than anything else, then I'd say it + cappuccino seems like a nice fit.
I'm really looking forward to Cappuccino staying alive for another ten years (and I wish all the luck to Objective-smalltalk's author) =). Though the recent Cappuccino conf doesn't feature many younger programmers.