It's great to see new developers! If you don't mind, I'd like to offer you some advice.
Default assets are fine! They work well and look great—I use them, too—but you should try decorating your Itch.io page. Figure out which color scheme fits the tone of your game and incorporate it into its overall vibe. Also, it's always good to try making a thumbnail in Photoshop. There's an online version that's identical to Photoshop called Photopea. Alternatively, you can use Ibispaint on a mobile device or drawing tablet. They have a large library of free tracing sketches, so creating something isn't too hard. It's mainly drag-and-drop, which is good if you don't feel like drawing. Good art takes time, so not feeling like drawing is a valid excuse.
Your game looks interesting, but the most important thing is visual identity. Once you've found yours, I'm sure you'll get the attention you deserve!
An interesting free font can make a good icon, so experiment! Another important thing to keep in mind is your description. A good description, list of features, story hook, or even a funny joke could mean the difference between a potential fan leaving and downloading. They say people eat with their eyes first, and that applies to games as well. When I started, my game icon was just a screenshot of the title screen, so it's best to take your time and build up your game's identity. Devlogs help, too. So go nuts!
Sorry if this comes off as pretentious or preachy. I just love this engine and want to see new developers succeed. Count me as your first review!