RNG is the bread and butter of this. The entire point of the game, building relationships, is based off talking points you may or may not get doing banal actions over and over. And the neanderthal MC can't hold more than a few talking point because his brain just doesn't function right, I guess? Just because it's was a small thing, doesn't mean it's not the majority of the game. If I have to repeat interactions just to possibly get another talking point to get another possible talking point to further the interactions, that's completely player unfriendly. It's time wasting for the sake of time wasting.
It was explained in a previous post but the topics you gain aren't really RNG. This explanation may not be 100% (and I don't feel like searching for the original post to confirm) but it is something along the lines of whenever it is possible to get a topic from some conversation/event it gets points added towards that topic. Whichever topic gets selected is based on whichever one has the most points (with maybe some small amount of RNG) and then those points get reset. But not all topics are equal and some get more points each time (or need fewer points accumulated to be gained?), so you will get them more often and you will get the rarer topics less often.
This isn't ever explained in game, so it definitely feels random, but you should be generally getting a topic every X number of times it is possible to get it, with X is based on the rarity of the topic. And when you don't get it, you have made progress towards getting it next time.
I think the game is still too grindy, and there can be real frustration when farming some rare topics or other interactions you need, but hopefully that reduces the frustration a bit from feeling that you just got unlucky on some chance to get a topic.
Edit: Turns out it is in the tutorial after all. Not sure if it was added to the tutorial since I played through it several years ago or if it was always there and I just forgot about it.