I find the people who have problems with Subaru fascinating because it's almost all for the same reasons. Either: he doesn't efficiently use RBD, he cries and whines A LOT, "lack" of character development, or some variation of these like "he's just generally retarded"
Looking at it from the perspective of Subaru being a realistic human MC I absolutely think he's one of if not the best representation. He's not a fantasy, he's not out to conquer the world, make a name for himself, have a harem, or play the "meta" of the Rezero world and his own abilities. Do people really find it hard to believe a man just wants what's best for himself and his loved ones?
Moreover it's taken some of you 10+ years to reach the mental/emotional state you're in. Subaru should reach it in a mere 1 or 2? Call me a fag but Subaru is a breathe of fresh air in a world of aura-farming and blatant power fetish main characters

tl;dr - Tappei is unironically Japan's best isekai writer