I can’t really comment on what to do about the existing project. If you are not having fun working on it, then I’d suggest you stop spending more time on it. If it’s in a playable state, you can “wrap it up” and polish everything you’ve added so far, and release it as-is.

Apart from that, as you’ve described yourself, learning to make games is an ever-changing process. You adopt new coding habits, have better ideas on how to make more complicated projects, explore new techniques to make something visually more fun etc.

The best way to learn, is to start by making small projects. For example trying to make a clone of a popular and simple game, like the original “Pong”. If you copy another game, that means you don’t have to worry about game design, and can focus on other parts of the project.

As you keep making more projects, there will be areas that you don’t have to focus anymore, and you’ll be able to work on more complicated projects. Also as you become comfortable programming, you can reach a point where handling a project of bigger scale can be simplified, so as to not feel as overwhelming. But all that comes with practice.

This is general advice for someone starting game development. I don’t know your exact experience/skills, but hope it will help in figuring out your next steps :)

At least I've also started coding, while mainly saving and continuing later, writing down my thoughts or stuff I'm planning later for adding, etc.

While motivation should be connected with fun-attributes, maybe either think of design / storyline / etc. as "chapters", working on the one that sounds awesome for this moment and let's get surprised how the game turns out?

Mine being mainly a concept that gets fused, parted, stopped still also published a while ago as prototype, then the platform wasn't hosting webgames (just mobile ones), one community didn't even reply and one declined mine because it's rather too focused on textlines than graphics. Recently I've still noticed this platform and published it, while inspiration came by a tribute of someone that gets the date fixed on the day I was releasing it.

In my case coding and releasing, same for the title, etc. being not just anything. It's how to get it perfect as I'm expecting it and being curious is other players even expecting a game like that being available. Probably those reasons could be motivating for keep on coding, or possibly if you find and get rid of bugs? Or the team-up with players could sound inspiring for either suiting with similar thoughts or receiving new ways of how to design visuals, audio or text there? Just thinking of where games could try to click for progressing in levels and exactly coding it with traps, so players have to find a more unique way ...would be just an option for a game that sounds not too common, nor hard to program, I guess?

If the project isn't fun to work on and you're not satisfied with where it's going, nothing says you have to finish it.  I've written off projects before because they turned into a quagmire or just weren't shaping up the way I wanted.  It's disappointing, but I still learned from the experience.

I didn't finish much of anything until I started doing game jams, which gave me a tight scope and a deadline to work in.  That gave me practice with scoping and finishing projects, which is a skill in itself.  Completing several small projects also let me make mistakes and learn from them in a small sandbox that would be over and done in a few weeks.  Then I do a better job on the next project and the next.  The more games I make, the more comfortable I get with making them, and the more I figure out the styles and techniques that work well for me.

There's no harm in putting it down and trying something new.  You can always come back to it later, if you want.