Could you talk more about this? This is completely different from my experience with the game. I thought the game was ok, not great, deserving of its 83 MC score but not at all deserving of it's many GotY nominations and even awards. I enjoyed the story and art direction but thought the combat was really poor, precisely because it always came down to matching stances. "Shield guy, shield stance, lance guy, lance stance, sword guy, sword stance". It was mindless, and as far as I could tell it was fake depth, not adding anything at all to the game. That's how I felt. But I would be very interested in learning if there's more to it, would be nice to understand the combat system better.
I did enjoy the one-on-one duel combat system A LOT, I wish the whole game had been based of that instead of playing Simon Says with stances. I always looked forward to every duel.
Sure, so the 'shield stance for shield guy' is just the basics of it so players would have an understanding of the system. But it's important to understand that what stances affect is stagger damage not actual damage. So the shield stance moves stagger shieldmen faster than others, but the actual damage is the same to everyone.
So for example, the Piercing Attack of Stone (Sword) stance is a really powerful attack that can kill most enemies in 1-2 hits (There's an upgrade that allows you to do it several times in a row). It works on absolutely every enemy. Heck, I killed spearmen more through this move than through spearstance because as long as you hit them (and it has to be targeted a bit), nobody has any way to defend themselves from it except shieldmen, who can still be hit with this move in the back or while they're preparing a shield attack.
Flurry Strike from Water (Shield) stance is a series of very fast attacks. Again, if you're in shield stance and you see not a shielded enemy, you can dodge and do a flurry strike to kill them quickly, even quicker than if you switch to spear stance!
Typhoon kicks, the special heavy attack of Wind (Spear) stance works on absolutely every normal-sized enemy (i.e. somebody who is not a brute), and there's an upgrade that adds the possibility for the enemies to remain stunned after the kick and you can one hit kill them. I used this frequently against really aggressive opponents from other stances.
Stuff like this. You don't have to switch stances to be 'more effective' against an opponents, in fact there's many reasons to NOT change stance. Like you know those Brutes who have a grenade launcher or something? They're bastards, a lot of the time you don't have enough time to stagger them with Moon/Brute Stance attacks. Just go into Sword stance and use piercing attack on them because they have literally 0 defence against that and are big targets that can't dodge.
This is the depth of the Stance system - because it affects only stagger damage, you actually have to mix and match stances to be more effective with ACTUAL damage.
The irony is that I decided to google at one point how many guides about stances talk about this... and I found only one. The rest teach only about the basics, but it's not how the system works. And one of the reason why Ghost of Tsushima unlocks stances one by one is not just for progression, but so you would use different moves against non-matching stances as well because you haven't yet unlocked their stance.
I can't post my video where I talk about this in-depth due to rules (and mods removed the link to the video in the original post), but in there you would see a lot of examples where I use unmatching stances to defeat enemies effectively.
And that's all if we touch just the Stance mechanic without going into Ghost Tools that add more dimensions to it.
It's really cool.