If you're comparing it to installation using an app store, where a new game can be installed with just a single tap, then yeah, you're right. For tech savvy people it's quite straightforward though: download, extract, install, and move a file. For everyone else it's a learning opportunity, but also, admittedly, a major inconvenience. Here are the reasons why the installation is not easier:
- Google doesn't want 18+ content on the Play Store, so the single tap solution is out of the picture.
- APK files for Ren'Py games can't be larger than 2GB. That's not enough for the amount of content the game has right now. Hence a workaround is needed, which is the big rpa file that you need to move during installation.
- That then means that you need at least 2 files to play the game + a file with installation instructions, so you need a zip file that bundles them together into a single download. But having that zip file adds yet another step to the installation process.
I have to admit, there are ways to streamline this, the status quo is pretty much an improvised solution. However, Android isn't the dev's priority right now: Google is looking to ban the installation of third-party apps, so right now the play is to wait and see before investing into a solution that potentially becomes obsolete very soon.
Sorry for the inconvenience.