I have to take issue with this. I've made several android apps, and they are NOT more difficult in general to create. The vast majority (though definitely not all) of the complexity comes from what you are trying to create, not the platform on which it was developed. You certainly could create an OctoPrint plugin that's easier to create than an android app, and vice versa.
For example, the last android app I created used GPS, an sqlite database, had built in messaging, communicated with a server, had configuration settings, custom map overlays, etc.. But, it was ALL written with Java. No HTML, no css, no knockout, python, no C++, no javascript, no gcode, etc. In a sense the barrier for entry was actually quite a bit lower than an OctoPrint plugin, especially if you have prior Java experience.
I paid for s3d and today I think it was mistake
I purchased S3D as well, but ONLY because my users were slicing with it, and I needed it for testing/development. For me this was a cost of supporting other users. I NEVER use this slicer for my own prints.
I also purchased a raspicam. Though they are cute, they are (arguably, of course) much less capable than similarly priced webcams. I was just tired of saying, "I don't know," when people asked for support. I will be able to re-purpose this camera for something fun, probably, and it wasn't too expensive, so that's good 
I dealt few days ago with a guy who complained that octoprint is to complex as he can't use gui to setup everything (wifi, ip addr..)
These complaints are the special sauce that allows us to create even better products. They direct us to problems we haven't yet solved, or new issues that our products have created. Obviously it's going to be difficult to configure wifi via a web GUI before there is a network connection, but it gives us a good example of how programs are always in constant need of improvement. It's an iterative process. If all plugins were one and done types of applications, there would be little need to have this discussion. Unfortunately all you have to do is look at the github issues for any particular plugin and you'll find lots of good reasons to continue to improve existing works. I'm not saying you disagree with this at all, just stressing the point.
This has been really interesting so far, and I'm glad we're having the conversation. So far I have to say that I'm leaning towards better user exposure to the various tipping mechanisms that already exist.