For myself personally, I don't have a problem with high level characters being able to survive a direct blast of fire from a dragon's mouth. ...
And this is the type of thing that I find absolutely immersion breaking.
The hit point bloat in D&D throws me every time.
It's not that hard for D&D/d20 to adjucate these type of situations.
You just make shields worth something more than a + to AC.
PC's gat to make a save vs. arrow/breath weapons if you have a med shield 1/2 damage - if you have a large shield you can duck behind, minimum damage.
Or something similar.
Things for d20/D&D get a whole lot more manageable if you fix HP at a low level. Yes you have to scale other parts of the system back, but then you also don't run into the scaling issues that HP bloat brings.
For nostalgia reason you can't really do that with D&D.
But sticking blindly to the HP bloat paradigm is one of the reasons why so many d20 based games got a reputation for not properly emulating the genre/IP they were being made for.