I’m currently in two different D&D campaigns. One plays combats on the regular 5ft grid, the other is “theatre of mind” where where everything is just described. Both are fine, I don’t really feel like I lose anything with either method, it’s just two different abstractions for the same ideas.
Larian’s previous game, Divinity Original Sin: 2, was still highly tactical despite its lack of grid-based positioning or targeting. The game used its mechanics of skills, freer movement, and surfaces/clouds to really shake up each battle and make them unique. Each combat was like a little puzzle. For me, who usually bounces off the likes of XCOM, it was absolutely brilliant. BG3 is much the same, just with a different ruleset (and I’m glad I was familiar with it beforehand. It must be daunting to be thrown into 5e without having a book thrown at you).
Being a nerd now, there is actually a grid in these games, but it’s only used for navmeshes and the surfaces. The game doesn’t expose either of these to you in-game. Visually, the edges of surfaces are messy and extend/retract from where they technically are according to the engine. I suppose you can kind of see the navmesh grid by clicking all around the edges of walkable areas, but other than walking up to edges, the navmesh has little impact on anything else.