The openness of the system is often praised as one of the main reasons for Android enthusiasts. You can install apps not only from the official store (Google Play) but also from other sources. But isn't that like running a Windows computer without a virus program?
Try to teach a person who really doesn't know anything about smartphones (except how to take photos, write messages and make phone calls) how to install an app from a source other than Google Play.... Difficult task, isn't it? But let me bet that this person knows how to install an app via Google Play? After all, the messenger for the messages must have somehow landed on the smartphone.
Whatever the source, be it F-Droid, a file from APKMirror or an apk file received via WhatsApp, it is quite an act for uninformed users to install this app. And worst of all, allowing third-party apps to be installed increases the security risk enormously.
Just recently, my mother called me and said her cell phone said she had a virus. But in the end it turned out that this was just a website that opened as a pop-up due to an advertisement on a news page. In bad spelling it was written there that the mobile phone was with a probability of 88.9% infected. She should press the button (which was extra large and flashing) to free her mobile phone from malware.
Thank God I was able to stop her from falling into this trap. If she had really clicked there, she would probably have downloaded an apk file and she would have installed it...
But in order not to expose themselves to the security risks mentioned above, many users do not activate the option to install third-party packages and only use Google Play. But Google Play has recently become more and more like the Apple App Store:
Recently, there has been an outcry in the developer community about Google Play. Because Google has changed the developer guidelines and no longer allows apps that use the Input Help API, but not to improve usability for people with disabilities.
Consequence? Some password managers were kicked out of the store because of their (very handy) autofill option, because Google thinks they should use the Autofill API. However, this API is only available since Android 8.0 and you remember the fragmentation problem...
That's why the question arises whether Android is also a walled garden due to the lack of serious alternatives to Google Play, as Apple's iOS is.