That's only the case for non essential upgrades though.
Getting at least some of the health and missile extensions really is not non-essential, not if you want to get anywhere that is...
But anyway, I don't remember the details, but I definitely remember getting stuck several times, without knowing where I should go to progress. I definitely remember some areas you had to find that were pretty well hidden... but regardless, the game basically requires that you memorize the entire map, so that when you get a powerup you know where to use it. Either that, or to re-explore everywhere every time you get one. The map's not much help for that, and the game doesn't have much helpful guide stuff like Metroid Prime, Fusion, or Zero Mission do, to tell you what direction you should be heading in. I really appreciated that Prime had that feature that told you what direction to head in... made it easier, maybe, but having to re-explore areas I've been every time I get a powerup just to check to see if there's a new area there gets frustrating.
I feel somewhat similarly about Zelda: LttP... it just doesn't give you enough clues for some of the things you are required to find (and there they really are required). Link's Awakening is a much better-designed game.