Now don't get me wrong.
I totally recommend that new players practice and focus on certain aspects of gameplay if they want to improve quickly.
Like if someone really want to improve quickly, you should basically physically handhold them to teach them how to micro their units effectively.
But it is not like a totally new RTS player are that likely to come up with a good list of gameplay aspects to focus on their own.
They might focus on defense or terraforming for example which are good skills to have in the end, but if they don't learn how to expand and be aggressive first, it might hamper their skills a lot if they dig down and porcs even harder to survive longer, instead of learning how to incorporate defenses and terraforming into an effective strategy that almost always requires focus on expansion and aggression first and foremost.