"Snakes. Why did it have to be *snakes*?"
Heh.
Courage isn't not being afraid, it's not being overcome by the fear. Failing a save vs the Frightened condition, is being overcome...
Failing the save against the dragon's breath weapon is hardly the end of the conflict. It's just 45 HP of damage.
Anything that's hp-denominated is not so bad, the way hps baloon for everyone in 5e...
...unless it's so much damage a failed save is instant death, of course.
And 5e did make a lot more effects use hps, which does make it seem more reasonable to have save go from bad to hopeless as you level... but, while attacks pretymuch always do damage, AC doesn't have the same issue as saves. You can wear armor, if youre a class that doesnt have decent armor or another feature and your ACs too low, you can take steps to improve it, without having to cover 5 other ACs, as well.
But you do need 6 saves, and there are still save effects that bypass hps.
Spending your 12th level feat to grab resilient gives you a +4 bump, +5 at the next level. Seems decent enough to me. If you want to make the argument that Resilient should give you 2 saves proficient instead of a +1 Stat bump, I'd have no problem agreeing with that.
Even if it did give you both a second important save and a second obscure one, you'd still have two non-proficient saves.
But, sure, half your feats is better than all of em.
I swear I remember asking this same question back in 2014 when this topic was raised here, but what, ideally, should the boundary be on BA? Failure rates should never be higher than 80%? 75%? I kind of feel like if 17,18, and 19 were supposed to be auto-successes in a BA system, they would have spelled that out.
I'm sure there's no solid line, but failing in a 19s gotta be on the wrong side of it.
It wouldn't take much to pull back from the precipice, 1/2 prof, prof-2. It'd still be falling behind on the majority of saves.
But, I suppose that might lead to monsters getting better saves...