In D&D 5e, the designed unit of play is the encounter. In the game designers’ attempt to build their game around an encounter environment, a lot of things that I liked from previous editions got trimmed, shortened, or nerfed. We won’t be changing any of the spells that exist in the game, much. Everything that is built around the encounter will remain for game balance reasons, mostly.
However, those encounter magics leave a lot of the flavor, the mystery, and the magic of magic on the designing-room floor. We will, in our world, have other kinds of magic… rituals and summonings and bargains… alchemy and potions and poultices… fey and djinn and demons.
Encounter magic is going to be rare. If a hamlet of 200 people has a wizard, that wizard likely doesn’t have any levels in the class of Wizard. It’s much more likely that such a small town’s wizard is something of an alchemist and herbalist who knows how to make a couple of different potions. The Master Wizard of a town of 750 people might have Class levels in Wizard (or Warlock or Sorcerer), maybe as many as three levels which would indicated something like the most powerful mystic in a hundred miles. This doesn’t mean they don’t possess a variety of arcane knowledges or skills. They often do, but it’s less academically rigid, more home-brewed sort of wisdom and hedge magic.
A magic user powerful enough to cast an actual fireball is a wizard who is smart enough to never cast a fireball while anyone’s around to witness it. Such events terrify the populace and the local leaders alike. Spell magics tend to be “foul” as they change the very nature of the environment around them. There may be people who claim to be such powerful magicians, but most of these are charlatans looking to extort locals for a nice living.
However… there are magics that are slow-builds toward powerful effects. Rituals that take hours, days, or weeks to perform… or years or decades. Potions that take a month to brew that can twist the fabric of the universe. These sorts of things exist, and running afoul of the kind of people who know such rituals and would seek to perform them is unwise for the common folk because people who are organized and patient enough to cast a ritual that takes a year tend to have plans in place to make disrupting such rituals difficult or deadly to those who might seek to do so. They also start innocently enough and largely go unnoticed until the rituals are quite advanced in their execution.
At the same time, magical effects can vary widely in their… effects. In the rules as they’re written, each spell or effect as a certain area of effect or target indicator. Especially with environmental effects… Light, Entangle, anything Thunderous… we will allow these effects to vary depending on the circumstance and what’s most dramatically appropriate. For example, in the RAW, the Light cantrip creates “bright” light in a 20′ radius with “dim” light another 20′ out, every single time it’s cast… If it’s more dramatically appropriate to have it be larger (like to illuminate the 100 orcs who are moving up on your position in the darkness) then we’ll allow that. Likewise, if it’s appropriate to be smaller, like you only need dim light for the thief to pick the lock then the Light cantrip is barley more than a candlelight…
This is not fair. I know. Fortunately, I don’t care about fair. I care about cool. If a spellcaster puts a lot of umph behind a spell… casts while angry or energetic… the effect may be larger. This is where role play will enhance the game directly… This will be at my discretion, and it’ll be as rare as magic is.
Lastly, magic brought the world as we know it into existence. So magics that are “goodly” tend to go unnoticed as they put the world right. Other magics can be sensed because they tend to change nature and foul the world around them. This leads to the understanding that magic is unnatural and “bad,” thus making those who use such magics “bad” too.