Do I really need to learn Loomis before I can draw from my imagination

>>2402702
You have to learn how to feel the form, experience it in order to convey it convincingly.

You have a lot of options besides Loomis, we just only said it always because is the most classic and easy to find in the internet.
You can try George Bridgman, the Draw with the Right Side by Betty Edwards if you are a full noob, Michael Hampton, etc.

And yes if you want to draw form imagination you have the learn that way, but what you get is to be a copy machine as you mention, in fact it is neither good or bad, but it has its disadvantages, such as when you want to do something you're bound to have a reference, which means eventually you'll lose time looking for the right to copy, when you could just build what like using your knowledge and use references to what are, for referrals.