Baldur's Gate 3 director Swen Vincke has shared the D&D spell that Larian most wanted to include but couldn't as it would have "doubled the size of the game" if they had.
In an interview with Dungeons & Dragons, Vincke was asked what he'd have liked to add to the game and the development stories that erupted from attempting to do so. His response was quick: "We wanted to do Dispel Magic."
In D&D, the spell's effect is pretty much as it sounds - you pick a target within range, cast the spell, and any magical effect attributed to that target ends (per a saving throw for higher level spells). Pretty much any spellcasting class in the game can learn it, and there's a huge amount of versatility attached to it; is an enemy Concentrating on a powerful spell? Are they drawing power from a magical item? Dispel Magic will stop them in their tracks.
Not every spell available in D&D features in Baldur's Gate 3 - several are absent because they were too OP to allow into the game - but Dispel Magic was "on the table for a long time, but it just became too much, because there's so much magic in the game." Vincke explains that internal playtesting always threw up the question of "'what if I come in and do Dispel Magic?'", causing plenty of headaches for the developers.
"There are still traces" of Dispel Magic in the game - much like the Exhaustion system - "where [developers] foresaw" the system and still wanted to play around it. Vincke says that "we wanted to do it, but it was just too much. It literally would have doubled the size of the game just to support that one spell properly."
The desire to support a feature "properly" is a recurring message from Vincke's interview, which he says might be his last from the Baldur's Gate 3 press trip. From giving Bards all of their bizarre Class Features to ensuring that your background is reflected in the game no matter how popular it is, it's clear that the Larian lead didn't want to leave any player behind.