Henadic Theologian
Legend
There’s a fair amount already in 5E.
This thread is helpful.
What should be brought forward...
4E skill challenges...though looser and better presented.
4E monster design.
4E clarity of the math behind the game.
4E monster types: minions, standard, elite, solo; monster roles: skirmisher, brute, soldier, etc; and the bloodied condition.
4E monster lore checks listed with the monsters.
4E encounter design.
4E classes like the warlord and the swordmage.
4E bonuses and scaling. Your level and training mattered more than your d20 roll after a certain point. That was nice.
4E World Axis cosmology.
4E Dawn War.
4E Nentir Vale and Points of Light.
4E split between rituals and combat magic.
4E residuum.
I loved almost everything about 4E except how clunky it played, how long it took to resolve combats, and near pure focus on combat.
The Dawn War I believe gets mentioned in the SCAG and DMG, but maybe it will come up more.
While Rituals are in the game, they didn't apply it to nearly enough spells, hence why a ton of utility spells never see use so more spells getting ritual caster is something I 100% support.