If there's only one enemy monster "theater of the mind" may work out.
You can see this, when actually doing a "one enemy monster fight" on a map. It's often very boring. The fighter/paladin/barbarian tanks all the damage, everyone goes to their position and never moves again. yawn
If there is more the one enemy monster, ranges are of importance. That is what a map is for.
The rules don't say:
You can cast this spell on everyone in [arms reach/initimate range/seeing the white of their eyes-range/view-sight in general].
It affects the target, and everyone in arms reach around them.
The rules say:
You can cast this spell on everyone in a 50ft range – it affects the target and everyone in a 10ft radius.
If you're not using a map when ranges are this specific you are bound to break rules, because you inadvertently will get a placement wrong. Especially when AoEs with ranges are involved it often becomes a huge clusterf*ck of "Ooof, who does this even hit? Who's in a 10ft radius?".
So it often ends in GMs being nice to their players and throwing the rules overboard, saying the spell hits everyone they want.
If DnD tells you: You can move 30ft, and the spell has 50ft range, but you're winging it, you're playing the wrong game.
Do it rarely: Okay, no need to change systems.
Do it all the time: Change to a system with less of a strategic element. You obviously don't care about movement-ranges.
There is no way to play the game wrong. I've also played a game where we didn't have Maps and it wasn't terribly difficult for the DM to keep notes on where everyone was and we just envisioned the whole thing in our mind. The thing about D&D that's wonderful is that the rules aren't absolute and really you can do whatever you want in fact they want you to go outside of the rules of the game and be creative which is why they have very few rules in the first place.