Random question time: other than what we´ve seen in the videos, have they announced or spoken about what kinds of items we might expect to see in the game? Knowing that would make it a bit easier to have an idea of where they´re going when it comes to exploration and progression.
I'm speaking about the QUALITY of side content, not the quantity 
And no, western sandbox aren't my thing.
Btw, the last Zelda with good side content was Wind Waker, imo.
Right. I updated my post and it counters your point right there. You just said that games with an open world developed in the west isn't your thing (which in and of itself I find a bit weird, I mean, it´s not like those games are all the same, unless you´re talking about Ubisoft games in which case I would completely agree), and that´s fine, that´s your subjective opinion.
That said, you might not enjoy GTA, but to say that its content is not filled to the brim with quality, or anything less than that is wrong, because there is more quality in those games than most games developed period. That said, it is completely fair to say that it´s not your thing, but that does´t reduce the objective quality of the work that was put into it. Obviously I can´t argue against a subjective opinion, but it does not sound like you´re the kind of guy who would be willing to step out of your comfort zone when it comes to games (obviously an assumption on my end), and unless you´ve actually played GTA and you can argue for as to why you think the quality of the side missions is less than favorable, I´d love to hear your thoughts.
To be fair though, Grand Theft Auto is sort of an end all example. There´s a reason it´s the best selling entertainment product in the history of entertainment (not a joke, look it up), and there´s a reason it´s got universal critical acclaim. I would not be willing to defend Assassin´s Creed Unity in the same context, for example. That game clearly likes quantity over quality.