I'd prefer upcasting remain, rather than the old as-you-level-the-spell-levels-too. It's just that leveled spells, as a limited resource should do more damage than they do now. Cantrip damage isn't too terribly bad, but that 8d6 fireball (28 ave.) at 5th level will just barely kill a 2014 bugbear (and not a 2024 one) . Back in older editions, dropping a 5d6 fireball (at 5th level) would kill a ~4 HD monster - basically an ogre (CR 2 nowadays, with 59 hp for the 2014 version and 68 now). Sadly, upleveling as it stands now is just worst as monster HP rapidly outpace spell damage output.
For me, spells should be a vote of "I want to end this monster right now" (or, "let's thin the herd so we can focus on the dangerous stuff"). They're limited resource, and as long as the DM isn't allowing 5MWD, their use should be something the spellcaster only drops after assessing the risk is too great to letting the martials beat it down. Most of the time, I'd rather see the spellcasters using combat cantrips, and only pulling out the "big guns" when things get desperate. But when those big guns go off, it should be noticeable and spectacular - not a drop in the bucket.
It sure feels like that was how 1e-2e handled it, but was lost by time 3E rolled around.
