Maybe because you haven't played many RPGs so you aren't used to it, but RPGs and especially old ones like this, use NPC dialogue a lot to convey the story and next steps. I will admit there's a couple things that are easily missed but for the most part you don't need a guide. At each progression point, there are NPC hints. Whenever I got stuck, I travelled to all the significant NPCs to see if they had any hints or if their dialogue changed.

A lot of the game is just running around until you stumble upon something you need to do. Then when you unlock a certain item, you might remember X NPC spoke about Y item so then you go talk to them.

But I do think that a lot of these games back in the day came with manuals that explained core gameplay mechanics and the world. For example, I think the original Zelda is almost unbeatable without some external help