The only way to improve is to keep at it! I know it's hard and usually very disheartening to not be able to create what you see in your head, but doing work with a goal like you are is honestly the best way to get better. I started my comic knowing my art wasn't where I wanted it to be, but within the last few months I've improved A LOT. For reference:
https://tapas.io/series/Ready-Spaghetti
And even though my comic isn't all that popular or even particularly well drawn, I have a goal to finish it.
HOWEVER. If you are struggling, and this is having a negative impact on your mental health, then you should stop or slow down.
But overall I find that working on your basics can come second after you find something you're passionate about completing. Maybe one day you'll decide to do a re-draw of your old comic pages and you'll be really grateful you completed it.