I'm a bit if the opposite, I seem to thrive on games that have a lot of collectibles and side missions/tasks because it turns into mindless fun between emails.
But I get where you're coming from, and I think that one of the game's pitfalls is the collectibles/side missions to main story ratio. Like finding the stickers/graffiti has been the most difficult for me, so I probably could have done without that one. The relics are really cool, and I love reading about them, but they kind of have a weird spread over the map.
I think the devs could have either made the map smaller (not that it's that large to begin with) with less "stuff", since you don't unlock at least half the map anyway if you just stick the main storyline, or they could have padded out or lengthened the main story so you do unlock all the map before you get to the point where you move "off map". (Edit to add) It seems like the devs got so caught up in creating a realistic version of Shibuya that it kinda got away from the main point and plot of the game.