I think his point was more the options to click on things shouldn't exist unless they do something. For example in the school you can click on Ryan's locker but it doesn't do anything yet. But you are right that the first week is very 'on rails' with the objective being to show the player how the game systems are set up without the player getting lost wondering what to do.I...have you actually played adventure games before? Like, at all?
The reason why it feels like an incomplete sandbox game...is because it's not a sandbox game nor was it meant to be. One of the earliest lessons that game developers had was that, sometimes, you can limit or outright sacrifice gameplay if it helps set or develop the characters in a game. It's why cutscenes exist at all.
You are, in effect, doing the equivalent of critizising the intro to Half-life 1 because it's 4 minutes of you being "trapped" in a train while the game takes you through a few panoramic scenes of the place where you were going to be playing in. It sets up a few things, like the fact that the MC is theoretical physicist, works in an underground experimental complex, the people in charge have an AWEFUL safety procedures or records, and the the place is HUGE.
You, on the other hand, would be mad because you weren't shooting people within the first few seconds of starting the game.
It's fine that you don't like it and that this is your opinion but none of it is actually legitimate criticism.
The game being a sand box or not is kind of an interesting question. I'm not sure if there's a term for this type of game or not yet. It's sort of like a sandbox in the sense you can wander around a world map as you please and complete events in different orders. But it's also like a VN in the sense the story is very linear. There are two main 'routes' and to progress you have to complete event chains. You going to be spending your time advancing the story not exploring the world. There aren't any side quests or secret locations behind a waterfall.
So sort of a mix between the two. The player is given more agency of their actions then a VN but is locked into a set of actions unlike a sandbox.
Renpy has a hard time with these sorts of hybrids but it's much easier for a new dev to learn then say Unity.
If people didn't hate RPGMaker so much I'd say that would be the best engine to use. NLT is probably the only dev that can get away with using it and only because he mods the fuck out of RPGM using %100 custom assets.