Swen mentions the tiered magic system of D&D as a "complicated" thing. Why he understimate the player base so much? Tiered magic system exists in TONS of games. Even Skyrim, which is extremely dumbed down uses it. You have novice -> apprentice -> adept -> expert -> master level of spells. My very first RPG was Might & Magic VII - For Blood and Honor and the game used the system >
I don't quite understand what he means by "complicated". He might just mean: unintuitive. In the clip, the comment is made after: "level 3 spell is out of range of level 4 Wizard". And, let's be fair, for uninitiated "why a level 4 Wizard can't cast a level 3 spell" is a legit question. Still, it is a problem of using same terms for different systems rather then the system itself being too complicated. And a good UI could help a lot when access to new levels spells are gained, what spells are what level etc. BG3 likes to throw everything into one bucket a bit too much for by taste.
That said, it is an odd complaint to come from the guy who leads a DnD project.