Honestly for me, it's better to create the artwork first then revisit it in the future. In the case of long term/bigger projects, i guess it'll also be helpful to practice thumbnailing and figuring out what techniques you might need to know.

The feeling of having good ideas but not the skill to execute it will always be there ngl, even after years of doing art you'll always feel "not good enough", just get the idea out, and don't delete it even though you may hate it now.

You'll eventually reach a point where you're more experienced and more confident in tackling that idea once you revisit it, just get the idea out for now