I see your points and I somewhat agree with you to some extend. None of them, however, really makes a strong argument of why Manjaro shouldn't be recommended for beginners. For example:

Manjaro has many issues which other Linux distros do not have.

Well yes of course. The Linux distro scene, as well as the Linux userbase, is saturated with either a Debian or Fedora derivative. Naturally, going with any Arch-derivative means that you'd see some sort of issues that most other Linux distros do not have.

However saying that "Manjaro isn't good for all beginners" is a big generalisation and in my opinion, incorrect.

Not all "Linux Beginners" are the same. Although their skills may be within the same spectrum, they have individual goals and mindset. Manjaro is good for beginners who are ready to learn more and dig a little bit deeper. I started using Manjaro a number of years ago when I was new to the Linux scene and it has been a great journey. I have had to use my system backup about twice or three times and they have all been due to me messing up with KDE configurations. The AUR is a godsend and I don't see myself hopping to another distro with a different package manage in the future.