Cantrips have a bit of a problem, but what's not clear is what it is. There are three rough categories of damage-dealing cantrips involved: (a) ranged cantrips that do scaling damage, (b) melee cantrips that do scaling damage, and (c) eldritch blast, which does a scaling number of attacks.
Originally, that last wasn't really a problem - Eldritch Blast is for Warlocks, and they are carefully constructed to be able to take advantage of it as a way to be a properly scaling ranged damage dealer. The fact that it scales slightly too wel isn't a big deal - being a warlock sacrifices a lot of the flexibility you get from other full-casters at high levels. But.. cantrips scale with class level, and the Warlock features that improve it can all be taken by a level 2 Warlock. That means that a 2-level dip into warlock is all a Charisma-caster needs to do very competitive long-range damage, giving rise to the Warlock-2/Sorcerer (quickened- blaster), the Warlock-2/Bard (blast-healer), and even the very strange Warlock-2/Wizard (swiss- army-blaster).
I discourage multi-classing in my games, and prefer to enable class-mixing via feats and archetypes, but those very feats and archetypes open up yet more optimizer holes - my warlock a-la-carte feats and Mystic Studies allow basically any character to pick up EB and Agonizing Blast without leaving their class, which lets the Arcana Cleric stack up Agonizing Blast and Potent Spellcasting to double-dip on the scaling blasts, or a Wizard to pick them both up scaling on Intelligence instead of Charisma.
That's.. not so awful, honestly. I prefer to allow that kind of flexibility, but it produces two problems: (a) it leads to most casters mostly casting Eldritch Blast, (b) I still feel that ranged DPR should be lower than melee DPR, because of the downsides involved with having to deal your damage from the area your target prefers to deal damage to.
This has been a rallying cry in many a reddit thread - EB is stronger than the other cantrips: make it less strong, so that a Warlock-2/Commoner-15 can't outdamage a Fighter-17.
There are a few obvious ways to do that - the simplest is to just make it like other cantrips, and do scaling damage instead of scaling strikes. Since that makes it basically Firebolt, we could up the damage die to a d12 to compensate. That's pretty simple, but it drops the damage a bit too far and takes away the specialness of EB.
Another solution is to make EB scale (unlike any other cantrip) with Warlock level. Then it would match the Fighter's Extra Attack feature, and incentivize people to actually play a full warlock occasionally (seriously, when was the last time you saw someone with more than 5 levels of warlock?)
That kind of shafts any non-warlock characters using it through feats though - I have a player in my current game that uses EB on a favored-soul, without doing any optimization work to boost it.
I think that, if I choose to weaken EB, I'd combine the two paths - it's not simple, but we can keep it viable (and not crazy) for non-warlocks while retaining it as a working Warlock damage build:
A beam of crackling energy streaks toward a creature within range. Make a ranged spell attack against the target. On a hit, the target takes 1d10 force damage. The spell does increased damage when you reach higher character levels: 2d10 at 5th level, 3d10 at 11th level, and 4d10 at 17th level. Alternatively, the spell creates more than one beam when you reach higher Warlock levels: two beams at 5th level, three beams at 11th level, and four beams at 17th level. You can direct the beams at the same target or at different ones. Make a separate attack roll for each beam.
This is only a good idea if you agree with the common opinion that cantrips are supposed to be weaker than attacks; that martial characters ought to have higher damage on their bread-and-butter attacks because they lack the capacity to do very high-damage spells occasionally.
The other approach to fixing the problem is to make the rest of the cantrips basically as good as eldritch blast. If we change all the scaling cantrips to do their damage multiple times, instead of dealing increasing damage (attack cantrips like Booming Blade and Greenflame Blade aside), then we reach parity again.
The downside to this approach is.. why play anything but a caster? It's already tough to justify most of the time, since casters have higher nova, area damage, and utility, but if we bring them all up to eldritch-blast level DPR, martial characters lose their one strength.
I'm going to implement the former in my game, though if my player prefers to keep her multi- blasting and never picks up any buffs for it, I won't bother her about it.