You don't have to westernize. (except for americans). I'm doing an unwesternized run as Bharat now, and am beating those westerners by numbers. You should only not expect to be able to conquer Europe without westernization, but any colony you will beat, and no one beats 60 heavies.
I am pretty sure someone like Path could 1-tag without westernizing. He 1-tagged Ryukyu in early 1700's, and the point differential on Indian or Chinese isn't enough to lose you 70 years. I don't see why a Chinese tech nation would struggle with 2-3 completed military ideas and current tech (I have done that, and still had admin efficiency).
What you lose out on is efficiency. The problem with westernization from a gameplay standpoint is that it creates screwy incentives. Normally, picking up disjointed territory in the Caucuses or vaulting downstream to snipe a European colony in Cape has only minimal upside. However, due to the contrived nature of tech groups and penalties, you have strong incentive to do otherwise completely wonky conquests. Blocking it as a European has similarly strange incentives, like only conquering small nations outright for the trade company and protectorate blocking, meaning that it's not viable to do what England did in India for example if you want to stop westernization and keep protectorates.
A lot of this could be solved if the old world nations had triggered modifiers or some other mechanic that allowed them to reduce technology cost as opposed to westernization. I don't care one bit for the selective-realism nonsense that's usually coughed up wrt westernization being "ahistorical" in this kind of game, but at the end of the day the gameplay incentives the current mechanic creates constrain your idea group choices unnecessarily and create nonsense incentives.
