People tend to think on black and white and not grayscale.
If you objectively compare the mechanics, writings and factions to fallout 4, Starfield is almost a direct upgrade from fallout 4 in several aspects. Gunplay, gun customization, rpg check choices that play more role in having a unique experience, factions that arent totally terribly written like it is in FO4, where almost all factions are unlikable or not interesting.
The people who are let down by starfield expected bethesda to not make a bethesda game in simple terms.
Do i think its GOTY material, hell no (im basically at the point of no return point in the game). Its a helluva lot better than FO4, but people treat the game like it killed their first child.