This might start some trouble, but I have noticed some broken things in 5e. Like the Tempest Cleric getting awesome bonuses to lightning spells, but no access to said spells. (Until level 3, call lightning once or twice a day) Real funny D&D.
How about the cleric inability to heal during combat? Yeah, burn your highest level spells to keep that Barbarian at max HP while a goblin with a stick undoes that work. Of course, they balance this by being able to heal yourself during short rests, or fighters healing a bit. Why not use a herbalism kit to spend 1/2 the GP and a weeks to brew a healing potion. Lame.
You mean non discrimination area effect spells in confined spaces with several team members around you? Sure, maximize those and watch 'em burn. Also, you used up those slots healing, right? A cantrip would be useless, you're right. What about level six, when your lightning attacks push enemies 10ft.?
This might start some trouble,

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.