Er, The third link doesn't even support your argument and the first two links are written by the same author.
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Signal IS much better.
It's a nonprofit, not a commerical company.
There are arguments for and against centralized systems and forks of apps. The lead dev of Signal is concerned about interoperability; but still leaves users the option of doing things the way they would like with the open source code; it's just not 'supported™'
Amongst many, many other factors, it's a nonprofit foundation, not a commercial company.
Long term, it has backing from people (like the original founders of Whatsapp) who want to see an open solution flourish. Plus people can donate.
Also, both the client and server are open source.