At the higher levels of play, StarCraft II is both skill and strategy. If your skill is what's holding you back, then yes, all you need is more practice. If it's your strategy, you could grind for a lifetime without improvement.

Couldn't strategic skill be improved? (Serious question. Don't know much about Starcraft. But for a game like chess, it was considered very possible to improve your skill in strategy)

I'm stuck in plat as well, but I really don't put that much time into best practices. Somehow my PvT has gotten better while my other two matches have gone down the drain.

It's too easy to watch top KR GM's stream and the hours just pass by.