The main issue for me is going to be the fact that narrative style doesn't give information about distances and positioning. Most spells used in battle still imply the use of a battle grid, and it also has issues regarding line of sight &c.
For example, if I wanted to Grease their frontline, I would have no idea where to drop it for maximum effect without getting an ally. If I wanted to take cover from their archers, I'd have no clue where to move because I don't know how they're positioned relative to me or where the nearest cover is. If I wanted to tag something from long range with a Fire Bolt, I wouldn't know whether it was close enough to hit.
For other characters, things like distance are crucial (can I move far enough to hit him in the same turn? How far do I need to move such that the enemy can't move and attack me in their next turn?).
What it comes down to is that when you don't have a battle grid... it opens up a lot of problems. Either you describe precisely in text the distances between every character and every other character as well as the relative positioning of major terrain features (which we don't do precisely because a battle grid is easier), or you... don't. That last one is incredibly unhealthy for the game because it invariably leads to misinterpretation (DM has one thing in mind when they write, players read something else) and impreciseness. This in turn slows down the game because just about every turn is going to have something along the lines of "Wait, how did that happen? I thought that-"
tl;dr
A battle grid is pretty much essential for two reasons: It removes uncertainty, and it speeds up the game. If you just go the simple route and color in cells in a spreadsheet with letters/numbers for characters and screenshot that, it's also much faster than writing up a comprehensive description of positioning. The fundamental truth is that D&D combat is built around the grid, and if you deviate from that you're leaving a whole lot up to DM fiat when you need to resolve unclear situations (which wouldn't have arisen with a grid), resulting in either upset players (because things seem to never go their way because they can't read the DM's mind) or bored players (because the DM tends to rule in their favor to avoid the first possibility).
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Mostly unrelated: The start of this combat was really, really messy. The raiders were a good distance away and were apparently alerted at the same time that Risey started to run. You apparently rolled initiative for the entire encounter, let Aldeth and Kawtari waste their actions on Risey, and then teleported Akira and all of the enemies on top of the rest of the party for what was effectively a full free round of combat. Given that the main body of the enemy was apparently running full tilt through the forest from several hundred feet away, it makes zero sense that a) they would have arrived in the handful of seconds that passed, or b) that nobody noticed them coming.
No offense, but that's sloppy, and it's the same issue of clarity that I was talking about above. You could have done several different things, depending on how you were interpreting the situation. Risey could have successfully escaped and then, a minute or so later, the raiders would have arrived and initiative would have been rolled. Or you could have rolled perception checks to see if anyone noticed them approaching, then rolled initiative and let people decide whether they wanted to keep going after Risey or deal with the new situation.
As it was, you took agency away from two people by taking their actions in the context of one situation (Risey's betrayal discovered, she attempts to flee, enemies are still distant) into another (enemies are right on top of us, initiative has been rolled) without letting anybody know that you were doing it. This screws over those players by essentially saying, "Sorry, you rolled highest initiative but you don't get to chose your first action for this combat," and for the party as a whole, "Some of you got initiative, but I'm going to fiat it so that the enemies basically get a free surprise round despite not surprising you."
Just some thoughts.