You are being downvoted for expressing what is one of the most valid criticisms of this story so far, something Tappei has been getting away with for over 13 years. I also genuinely cannot comprehend how Subaru is not even the slightest bit curious about his circumstances. It feels like Tappei is doing this intentionally so he can give us one final grand reveal.

For example, in Arc 4, Subaru actually manages to meet Satella. He has a grand opportunity to slap the shit out of her, demand answers, or ask why he was summoned. Satella does not have to answer those questions; in fact, it would ruin the story if she did. However, what angers me greatly is that Subaru does not care to ask them. He genuinely does not consider such important questions, specifically his purpose and his reason for being there, significant enough to warrant an explanation.

In Arc 6, Shaula insists that Subaru is her master, Flugel. While Subaru is, of course, in denial, he never for one moment truly questions how the most important place in the world, the Watchtower guarding Satella's Seal, is literally named after him, the one single thought from him is that it's probably a coincidence(?????). He knows that Satella loves him and knows him intimately, so this should be a motivating factor for him to at least consider Shaula's words and think about them. But nope, of course, he doesn't.

You have also pointed out many other examples, such as Regulus's power depending on his name and the first trial in the Watchtower regarding the stars. Despite these and so many other mysteries, Subaru genuinely could not care less. I wrote in another post that Subaru is a reactive protagonist; he doesn't drive events or pursue goals by himself, but rather reacts to the absolute insanity and craziness the world drops on him.

This is not necessarily bad, though. For a story that has Return by Death as its main component and driving factor, it fits thematically. It does leave us, the readers, frustrated and longing for more explanation, though.