Requires ammo and takes carry weight
Have you actually played a 5e campaign where ammo tracking and carry weight so crippled whoever was playing an Archery Fighter/Ranger or Rogue that the Wizard and Cleric ruled the show with their cantrips?
Until you hit 3rd, the difference between 1d10 (5.5) and 1d8 + 3 (7.5) is still less wide than that "half damage" you're purporting.
Duelist would be d8 + 5 (9.5) , which is much closer to double d10 (5.5). Same with the rogue's 2d6 + 3 (10). An Archery Fighter gets +10% to hit, which significantly increases effective damage as well. Your rules knowledge is poor.
And since we were talking about
scaling, it makes more sense to look where things start to
scale. 1st level is precisely where the cantrip should be the most useful; it's the level where the wizard has so few spell slots that he'd otherwise be better off staying home and telling the party to call him once everyone hits level 3.
casters can very well sweep more low level foes from the board with single cantrips than the strikers
If you present the players with so many tightly clustered goblins and kobolds that the 17th wizard's ability to do 3d6 damage in a 2x2 grid is able to kill things at such a high rate that the Barbarian feels useless by comparison, the wizard will kill 4 kobolds in Round 1, and in Round 2, the remaining 124 kobolds will kill him.
Experience beats theorycraft every time, because when you just try to play the game in your head using a calculator, you forget one thing after another, after another. I bet in 10 years of running the game, I saw high-level wizards use cantrips less than a dozen times. Meanwhile, I have actually experienced low-level casters in classic D&D editions & OSR games who were so bored they were ready to quit the game.
Real problems are more important to solve than fictional problems. If you can describe for me a
real campaign that
actually broke down because the wizard had Fire Bolt or Poison Spray, I'm all ears.