@Melooon bringing the dedicated artist study vibe!
As third person though, I have to say it makes it sound like a lot. I think it's fair to just play around with software and metaphorically put the puzzle pieces together until you find something that fits
Like okay, I make this cube move now from left to right. Now how do I make it shoot? Next, how do I apply a texture to it? Now, how would I create an environment? How do I make text appear in a text bubble? etc. and then you start replacing things, refactoring things, as your skills improve and you wanna change something.
Look at Stardew Valley creator Eric Barone - SDV was created solely by him, for years before the release, and old trailers and images are still out there. The old versions are nowhere near as polished as the final product that went over countless iterations, suggestions by others, a publisher etc. so it's just natural to always build on top of what you created.
For the beginning and to learn the basics, I think it matters less if it's a game that you would actually like to play or that would make money in any way - just something that gets you to research the things you wanna do. It's similar to website building, where adding on to it makes you increase your skills because you start to think, well, how can I maybe tilt this text?
If you do wanna work on your first dedicated project that should be worth presenting or something you enjoy, I think Melon's approach could be great. Though I laughed at
Go to a desert
Just go to your nearest desert, duh. If you want to make a game about space, go to the moon