Eh. I think characters dying as the only stakes is weak writing anyway. If I were using that as a judgement, all of Star Wars is terrible, especially the Clone Wars. Obviously, that's not the case. Besides, clearly the armor rating is meaningless given the events of the S2 finale -- clearly the armor isn't protecting him from impacts what with his head injury.
We if look to Ming Na Wen's character I'd even argue that being hit by blasters in New Star Wars is just an opportunity to visit the medic anyway, so Din wearing beskar doesn't really remove any of the suspense for me.
I think there's a wide spread. I'd say that there's westerns like Brokeback Mountain and Dances With Wolves, where the suspense is more from the dire circumstances and grit that they have to work through in order to survive -- few times are their lives gravely endangered. Similarly, there's the Clint Eastwood westerns where you don't really expect anything to be happening to that main character, yet they're still well received. The "True Grit" style Western -- someone to protect while you rough it through the hard life.
And then there's the westerns you're talking about, The Good The Bad and The Ugly, nearly Magnificent Seven style western where the characters present an archetype and have a fatal flaw that leads to their downfall.
The Mandalorian is more like a Western of the Week TV show where you have the drama of the grit, an undercurrent of hope that's played off the main characters hardships.
Idk. Din being invincible in the show is seemingly irrelevant to me, and not even supported in the content of the show. The first two seasons definitely have space Western episodes though, even if they might not be the more typical main character on the verge of death style ones.