I'll understand if you aren't a hardware person, but I think you severely overestimate how complex a drone needs to be if you only intend for it to be single use (which is apparently all the rage in modern war).
You don't even need drone specific parts, the parts you need are used in all kinds of other applications...many are even in your home right now whether you know it or not.
To destroy the supply of these generic parts you would have to destroy...basically everything.
> Then why weren't they widely used in the first world war?
This statement alone makes me not take your argument seriously. You aren't arguing in good faith.