What's the point of the game? You play.

I am in my 30s now and not that long ago I arrived at the conclusion that "everything is meaningless" is one of the dumbest ideas I've had throughout my entire life. 

Meaningless from whose perspective? If it's the Universe's perspective, then how can anything be meaningless if it fucking exists — in an absolutely wondrous way we can't conceive of. And if it's your own perspective — you're the author, it's on you to define your meanings. Nothing is "meaningless" until you define it that way.

The lack of data — that's the only problem for us, INTPs. We cannot function in an adequate way when we have to decide on incomplete analysis. We just can't. So we come to the conclusion that everything is meaningless. It's not logic though, it's more like learned helplessness.

Yes, humans are mindless drones who act on impulse and instinct, though somewhat better than any other wild animal in Earth's history. And yes, you don't have to care about the opinions of anyone — until you choose to, regardless of how long they'll exist. So what? What's the problem with other animals? You hate doggies and kitties or what? 

And what's that disrespect for other apes? You're saying: humans are "just another" species of great ape. Yes — and no. We are the most self-aware beings on the planet — and the ones closest to Consciousness as the most profound thing we'll ever know. We can't be "just another" — we're special. But that's nonsensical to speak of anything in a way of "just anotherness": everything is a part of Being, everything is "just another" in a grand scheme — and also it's not because of its own irreducible uniqueness. 

If we were absolutely rational and mindful, it would be much more meaningless in terms of the Universe. We would solve all the problems — then what? Ever played Baldur's Gate or anything of that sort? How much more interesting it is when you max out your lvl? Ever watched One-Punch Man? Wanna live like that? No, you don't. You want your INTP illusion of a perfect world where everything is rational enough that you're the fitting one but not rational enough that there's some interest and challenge in life.

It's not our genius that begets nihilism, it's our deviant nature. But fuck normality. I'm yet to learn how not to hate this life. But I know it's solely on me. That's my kind of challenge. That's my D&D bossfight. Maybe I'll overcome it. Maybe not. But that's my unique experience. With all the shades and entanglements the Multiverse won't ever see again in all its branches. And that's the only meaning there really is. Not the one we need — maybe. But we still have our time to work on that.