The problem with subtle is potentially the visual clues on opponents.
Not to say that one shouldn't strive for a balance.
But visual feedback still works even if it's not on all the time. E.g. someone has Fire Resistance / Protection from Elements or such on (whatever it is in 5e). You hit them with a fire attack and energy flashes and absorbs the fire. That would actually be more
clear than having some sparks flying 24/7 that don't even react to fire (like NWN).
But the absolute worst is when you spend a lot of time customizing the look of your Wizard, only for them to be a sparkling pulsating force bubble mess 24/7 and you can't even see the character model anymore.
How come NPC's don't react to that obscuring mess during dialogue?
I'm not sure all magical protections even should
be visualized. A big part of the usefulness of a protection spell is that your enemies don't know about it
. If they do, they can always choose to target another party member who doesn't have it. And this should work both ways.
Maybe even give Detect Magic a purpose, revealing those auras and protections?