That's nothing in cosmic timescales and it's less than half the lifetime of the oldest organism on Earth, but it only SEEMS vast to humans. Even human societies behave more or less along the path towards resource maximalization, and thus act far beyond the scope of single lifetimes.
Who exactly will be making these 100,000-year plans if not humans? Most of us have ridiculously short time horizons. We are REALLY bad at delaying immeadiate gratification for potential future gain. Planning for retirement is the most far-reaching thing most humans will ever even consider, and how does that go for everyone? And most organizational/governmental time scales are ironically far shorter than that. You might think that we would overcome that, but do you think the average American's time horizon has increased or decresed over the last 100 years?
These scenarios assume future us will be WAY better at everything than current us.
If future us continues to advance, we'll have surely better tech, but why assume that we'll have the will to spend a huge amount of resources today on massive gambles that will only have a chance to pay off thousands of years after we're dead? Imagine an Egyptian pharoah thinking, "well, I was going to build this awesome-ass pyramid, but instead, lets plant this seed that will help FOHers shitpost in a few thousand years!"
Even if our tech improves in almost unimaginable ways, it will still be humans making the decisions. And we want stuff now. And wanting stuff now does not mesh with really long trips. We stood on the moon before most of us were born, and we haven't even been to Mars yet (and arguably, can't even go back to the moon at the moment). The great colonizers indeed!
The great filter is us.
We've had nuclear power for less than 100 years without managing to hit the reset button on modern society, albeit with a few close calls. All of this is predicated on our tech advancing, but the ease with which destruction can be brough about naturally follows. Most countries could have nukes now, if we would let them. How long until it's easy enough that we can't stop them? How long until someone really builds a cobolt boat? A sufficiently motivated billionaire might be able to push the reset button today (arguably, that's being attempted right now). How long until randos can start CRISPRing plagues in their basement?
I don't think that's as pessimistic as it sounds though. I think there's a pretty high chance that the next hundred or two years will be really amazing. 50 million though? On galactic time scales, there's just too much that can go wrong.