Welcome to our community!
I have been drawing for many years, and I still find it difficult to get nice lines with a graphic tablet, which is the reason why I mainly paint on my computer. I also bought a tool named Lazy Nezumi (or something like that), which is helpful for drawing nicer lines which don’t look that scribbly. ClipStudio Paint is also nice for drawing.
However, in the end, there is just one way to improve your drawings with your graphic pad: by drawing with your graphic pad. Knowing how to draw is just one aspect. You also need to get used to your tool.
Don’t worry if your digital sketches don’t significantly improve. Draw on paper instead to improve your skills and try to occasionally draw with your graphic pad to see if your sketches start looking nicer.
In my personal opinion, your pen strokes look fine. If you keep practising, they’ll improve further over time.