Must the game explain itself? It's a third installment in a series, taking place in an established setting. A lot has changed since BG1 and 2, but the basic knowledge (e.g. about Baldur's Gate the city) from those games is still applicable to BG3. You don't pick up a random adventure module and expect it to explain every minute detail, like how common druids are, about its world.
The counterexamples you give are quite confusing. Inquisition has a bombastic opening, and I can't see how anything after that will give you a sense of what's normal in the setting if you're coming into it completely blank. The whole game is nothing but a mess of extraordinary circumstances and factions you have little context for if you're not reading the codex. Not helping the situation is the general sloppiness of the plot: for example, was the conflict between the mages and the templars really that important if it's resolved practically offscreen? Overall, Inquisition is not a game I'd recommend anyone to go into blind (or at all, to be honest), it needs at least the context of Origins, where all the factions and their basic dilemmas are showcased.
Wrath, on the other hand, is a very straightforward story. A person with minimal knowledge of basic tropes will be able to grasp it. Sword & sorcery, demons = bad, demons are attacking, kill demons. Everything beyond that is fluff, but even so, a good 70% of dialogue in Wrath is expository in nature. You'll be asking everyone who, what, where, when, and why over and over, and maybe if you're lucky you'll get an alignment option to actually roleplay. It becomes absurd at times, how you can stand in the middle of a field and go down a list of questions like an automaton, interrogating a demon whose only desire is to tear you apart and defile the remains. He has no reason to answer, yet for some reason he does. It's very mechanical, hardly something to emulate.
I understand that for a lot of people BG3 is going to be their first BG game, and probably their first DnD game, but I can't say that modeling dialogue to cater to people who pick up the third book in a series and then act surprised when they don't understand what's going on in the world is a good idea. A baseline level of knowledge has to be assumed.
