I would recommend to read the article first and then follow the protectionism in the comments later.
The main claim of the article is that we need federation, as we do with the email (but imo we are loosing it).
In addition, Signal shares a problem with email - information about your communication circle is not secure.
Instead we should discuss why these are not implemented and how could be proceed to implement them.
If you want to discuss how a follow-on from Signal could and maybe should address some or all of those points, great! That's a conversation worth having. But it doesn't sound from your toplevel comment as though it is the conversation you're trying to start.
This is mis-categorisation. The article says "I won't recommend the use of Signal" and gives reasons and desired improvements.
I think that you are misinterpreting the articles intention. It is more complex than a single statement. I believe that the author wants Signal to change in certain direction. It is hard to do when the userbase is growing regardless and people are not aware of the issues.
For example someone may make a false impression that because the messenger uses the signal protocol, it is secure (and points to this paper), but in fact its implementation makes it considerably less secure.