Apparently you've forgotten (or written in ignorance) that Larian attempted to incorporate a day/night schedule with NPC schedules in DOS1 but ultimately gave up on account of the complexity, so they know as well as anyone what kind of resources it would require to implement it. The decision to reject it is well informed and not silly.
Whatever Sven does I know it will be fine. Never have I seen a game developer so obviously enthusiastic about his job, who so much clearly enjoys the company of other people, as I have seen in Sven. You cannot fake the sort of enthusiasm he brings to his many videos about Larian's work. He's a joy to watch and listen to, even if his enthusiasm propels his speech at a 90 miles-per-hour clip as if he's scared he's going to run out of time...;) He's an example to the rest of them, imo.
But that doesn't mean he's perfect, and Sven seems the kind of level-headed guy who'd agree that none of us are...;) IIRC, in the first game, day-night was a stretch goal, wasn't it? His arguments made plenty of sense then as the game foundation was already laid and it was too late to rewrite the engine to properly do day-night. Fine, that was certainly understandable...then, and for D:OS exclusively.
But this is a brand-new game, ostensibly getting a brand-new engine. That was my point. If ever there was a time to bring day-night to Divinity it is now. Because, if not now, when, then?