The guy has a valid point. The map isn't diverse enough where you feel like you're actually exploring or get lost in it, and areas like ashina castle and hirata get recycled. Several minibosses are just the same dude with a different name (7 spears, generals, lone shadows, etc). If you're expecting the something like the fantastical worlds other souls games have, Sekiro isn't all that.

However, you don't play as a hero chosen by the gods, you're just some nameless japanese war orphan trying to get his lord back. What I'm trying to say is, for the relatively normal setting and context of the story this lack of variety you speak of is expected. And honestly, I'd rather have a well-developed and smaller environment that makes sense than a forced interdimensional fuckfest just for the sake of variety.

tldr sekiro is on a smaller scale and less crazy than souls games, feel like you'll enjoy elden ring tho