You will not do maths casually until you have memorized enough multiplication to make it not torture. You will not pick up multiplication from using a calculator any more than you will pick up programming from using a computer.
> native speakers of a language will conjugate correctly without memorising
They do not. They have memorized, through massive, constant, and forced practice, and now they conjugate correctly. The alternative of consulting a computer every time they need to speak is not a realistic one.