I know there is one by Victor Engine but I don't think that it's compatible with Yanfly's plugins.
I know it's since been discussed, but I'm not sure where you got this idea. I have several plugins by both authors in my project and they work just fine (as well as stuff from SRD and HimeWorks).
I wonder why you keep asking "Should I make this plugin" rather than
just make it, and release/sell it?
I agree with this.
I want to "gauge the popularity" of the plugin because of the above 2 reasons.
Most of the time when a plugin gets used, it's because someone is searching for that functionality. I think you have a much lower chance of people who are already using what they want in their projects seeing your random posts and getting inspired to say "Oh, yeah, that never occurred to me but I could use it!"
The plugins are rather "bare bones" and can be extended a lot.
To me, that is a problem. If a plugin is simple and bare bones, that means I (or any competent coder) could duplicate it easily, and perhaps a competent RPG Maker user could even duplicate it via eventing. That's not worth paying for.
I have paid for plugins that are sufficiently complex that in order to code the effects on my own, it would take significant research into the engine or significant time because it's a large plugin with a lot of code.
Also, just my opinion but if your plugin is "bare bones" as you call it, I'm not seeing why people would pay money for that. If I'm going to buy a plugin, it's gotta be polished, and it's gotta be something I really need/want for my game.
This.
Oh making each of these plugins "polished" will take a lot of time and a lot of hard work for me. It would be neither for me if I was a better RMMV plugin creator. But it is also difficult for me to do all this learning and plugin development. I would rather create basic plugins for a hobby, for fun, and to learn more but I also want to make some money off of them. What should I do?
That...is not really how the world works.

People don't get paid money for amateur efforts that they're learning as a hobby.
Would you pay someone who says "I'm learning how to change my oil in my own garage, but do you want to pay me to fix your car?" Or "I'm teaching myself using tablature to play the guitar, but do you want to pay me to play for your wedding?" Or "Here are these bare bones stick figures I can draw, would you pay me to use them in your game?"
People get paid money for things because they have spent a significant amount of time in their life learning how to do it well, and therefore they're doing something that the average person
can't do. You don't just get to say "I want to make some money off of this" and magically it happens.
I'm not an expert in this system as I have only played the FF7 Remake but this is the best I can tell you right now. Maybe the original FF7 was somewhat different. I would love anyone who knows these 2 games to help me out explain these things.
I would consider this a bit of a problem, also. You're trying to gauge interest in this plugin before you start making it, but you don't even know what it would do? Even though I disagree with the whole "gauging interest" approach, you should have a defined idea and vision in your head and be able to explain what your plugin would do. Why would anyone else care about you doing kind of something maybe that you need explained?
