If I can make one or two comments about the effect of cantrips on combat...
A lot of the actual play of cantrips depends greatly on party composition. In our AD&D game which ran from 2013-2015 while waiting for 5E to come out), the front rank of the party (3 characters) formed a defensive line behind which the rest of the group sat. A cleric in AD&D had no missile weapons to speak of, so if they weren't in that front rank, they basically cast bless and waited for the combat to end. That was with nine characters - PCs and henchmen.
In our D&D 5E games, a more typical party size is 4 characters. In that situation, the archetypal group of a fighter, cleric, rogue and wizard ends up with the fighter and cleric in melee, while the rogue and wizard are behind. With such a composition the use of cleric cantrips in combat becomes more problematic.
Beside, what cantrips are we talking about? I find this a major flaw in the argument that cantrips turn everyone into faux-wizards. Quite simply, most classes don't have (per the PHB) access to a good selection of attack cantrips.
Let's look at them:
Bard: Vicious Mockery
Cleric: Sacred Flame
Druid: Poison Spray, Produce Flame, Shillelagh, Thorn Whip
Sorcerer: Acid Splash, Chill Touch, Fire Bolt, Poison Spray, Ray of Frost, Shocking Grasp
Warlock: Chill Touch, Eldritch Blast, Poison Spray
Wizard: Acid Splash, Chill Touch, Fire Bolt, Poison Spray, Ray of Frost, Shocking Grasp
Just by examining the spell lists, it quickly becomes obvious that neither the Bard nor Cleric are at their best when just spamming cantrips. If the Bard actually wishes to deal significant damage, a bow or rapier is far more effective. Likewise, the Cleric has sacred flame, which at least deals damage, but against a significant number of creatures is not as effective as a weapon. Certainly at lower levels, your chances of hitting with a melee weapon are better than a monster failing a saving throw against sacred flame. There are situation where it is superior, but it isn't universally better than a weapon attack.
For the Sorcerer, Warlock and Wizard: They're wizards in any case. This is what they should be doing. I'll leave aside whether it is a good thing or not save to say that if in AD&D all Wizards were using wands of magic missile and wands of fire... then cantrips have simply taken the place of the wands.
Which brings us to the one class where cantrips do change how we perceive the class. Or, perhaps I should say, how some of us perceive the class. Historically, the druid gained spellcasting capabilities faster than any class in AD&D. They weren't a top-rank melee combatant - where the potential AC of the character made the most difference to their effectiveness. Clerics and Fighters were in plate armour and could stand toe-to-toe. The druid, in leather and shield, could not. (Barkskin improved AC by 1. It wasn't that good).
The fact is that a first-level druid was pretty awful. Yes, they got two spells (plus Wisdom modifier), but their first-level spells were forgettable - with the exception of animal friendship, which allowed them to take a wolf as a pet. So, as a first-level druid, you were really playing a wolf and his human side-kick! Honestly, this didn't change for many levels, even with their fast gaining of spells, they weren't getting all that many significant ones. (Call lighting? Awesome... but it required a storm).
The druid came into its own in 3E. A little too much so! Animal companion, shape-shifting, good utility spells and a fair number of attack spells...
So, I think there's a definite argument to saying the 5E druid changes how it is played. I am not, however, convinced that this is a bad thing. My experience with druids in my games indicate that (a) shapechanging trumps cantrip use and (b) shillelagh is awesome.
Cheers!