Agreed with article, but for ordinary users I would have much easier to understand reasons why I ditched Signal some time ago after years of use:
1. It's unreliable, if you switch between mobile network and WiFi connection it takes way long time for Signal to register to change to send/receive the messages, while Whatsapp has no such problem and send message almost instantly.
2. Devs ignore users, I waited years for file picker being able to provide such BASIC feature as selecting multiple pictures at once, for years you have to select pictures one by one, Signal devs remind of Firefox devs, zero interest in fixing basic things.
3. It's unreliable poorly operated service, I remember when Signal went down and it took almost whole night in US until someone in US woke up and fixed it, I was for hours without working service.
4. The last drop was when they started ti push on users some PIN code nobody asked for taking 1/3 of the screen until you created it, for some users full screen nag. Then I decided to move me and my wife and both of my parents from Signal, so good luck with such crappy service (I know they soon backpedalled from this stupid decision but it was already way too late for us and they lost at least 4 users).
5. It's user hostile - there is no way knowing long pressing Send button allows you to force send message as SMS to Signal user, there was no introduction at first launch explaining this to user, each and every user have to go to Google and search how to do this. I assume also there is no automatic SMS fallback for Signal messages which are not sent/delivered within specific time frame.
6. There is no 3rd party app allowed, so you are stuck with one option whether you like it or not despite their "open source" claims.
All these happened before it became hype and fashionable to be on Signal, so maybe it's different now, but these are basic things ordinary users care about who don't even really care all that much about privacy and other stuff.
If you want to use alternative service you better use Element (Matrix), it doesn't require phone number, it doesn't rely on one American controlled server.