Okay, replayed Planescape Torment about a year ago, it is still fresh on my mind so I can make a comparison. The major differences in terms of writing is that Planescape: Torment worries with where the player is at that moment and what the player sees. NumaNuma worries with where the player should go and pay little attention with where he is, it is more interested into pushing the player into the plot while Planescape Torment has its plot around the player for him to discover. One only cares into pushing the player forward and the other is more passive trying to lure the player on its mystery first, one has patience and the other doesn't, one cares about the player, the other cares about the plot.
I dunno if this is a question of talent or that game designers now work on their niche and writers on their other little niche like Infinitron said, NumaNuma worries a lot about informing the player while Planescape Torment worries a lot about luring the player and on the process inform him very, very slowly, on a much more passive way.
There are huge differences on those approaches, on Planescape Torment, for example, you find a major character that is later central to he plot on the Mortuary, Deionarra, you can find her out of your organic exploration, there is nothing guiding you to her and pushing you forward, the only goal is to leave the Mortuary, same you can find there one of the companions of your past and see at first hand how you were ruthless.
You unravel things and the player only come to know things out of his exploration, the characters only give you fragmented information based on their points of view. I remember when I first played and the Nameless one wake up on the mortuary, you only know you wrote a message to yourself on your back on a certain desperate tone, that you need to find Pharod and Morte while being helpful and sympathetic, it isn't being 100% honest with you for some reason.
Right after you wake up, you have the whole Mortuary, a weird place, you get to know of the Dustmen and how they see death, what is something extremely important as the Mortuary is the place you are going to be returning with a certain frequency. After you are done exploring the Mortuary, you had an awesome introduction not only to the setting but to your condition right of the bat. You won't have much in terms of exposition of what happened but you get learn a lot about where you are right now.
Later on, this tendency of giving the player just a little prod on a direction and let him figure out the details was really well done. You go exploring not only to see side content but get to learn about yourself, like when you go to that tavern in Planescape: Torment and meet Ignus and Dakkon, you feel you need to explore not to only consume content on a mindless way but that each location might have some tiny clue about you.
It is said that on video-games, the player is the king, this can be grossly misunderstood as the need to pander the player and threat him like a capricious child that need validation but if this is ignored and you as a writer is more worried about your grand story and not much how the player experiences it, this isn't good too.
In Numanuma, your situation is clear from the start and there is little for you to discover exploring. I got surprised how optional the entire content on Sagus is and how quickly you get to know everything you need to know and are pushed on the next location. The plot is in such a hurry to give you information and push you forward. You get to know who the Changing God is, who the Sorrow is, the castoffs and all of that on the first 10 minutes of the game that the rest of Sagus Cliff is kinda irrelevant and you only explore it to level up and consume side content.
Worse, they give you exposition on Sagus Cliff about things that will only be relevant much later while they pay little attention to where the player actually is, the Sagus city itself. There is no decent introduction where you are, no decent introduction towards the setting and its rules, too much exposition that could be easily delayed for when it is relevant but is regurgitated to the player when the player couldn't care less and wish to know more about the place he is.
