It makes a lot of sense. Whoever wants to continue developing "these apps" will do it privately, and sell the service to those who want to keep doing things in hiding. Well done, watchdog!
So again, it just harms the general public, while making it harder to catch criminals.
It makes it easier to catch criminals, since anyone who has the app is a criminal. I believe they already treat GrapheneOS this way.
Actually it opens them up to being phished by the government. There have been several high profile cases where because of searching for custom communication services, groups ended up being vulnerable.
It's simpler than that. OSS strong encryption tools are available than anyone can run on the command line to encrypt their messages, which can then just go as attachments via email, whatsapp, etc. No new developers required. And as you say, the general public have to suffer with weak encryption while those who really want to encrypt do so regardless.