^Here's the one big thing you have to consider, though: by all technicality, we are in a hurry to leave our planet. It's hard to think of when NASA funding is so low (even with SpaceX and Blue Origin in the news so often), but think more long-term. Consider we started putting humans into space a little over half a century ago and we're trying to enter an environment so thickly hostile to life itself that we actually write horror stories about it.
We're basing these predictions off the idea that other species must have become super-enlightened one day and then, five years later, were already exploring the cosmos. Chances are, most ETIs have had a similar experience to us— they gradually developed more and more capable technology over the centuries, then discovered that they could ride explosions outside their planet's atmosphere (providing they don't live on some supermagnetic planet somehow and could just lift themselves into space with enough magnetite), and things progressed either at an accelerated rate... or they lollygagged just as we "are". Perhaps their governments or corporations or fiefdoms or whathaveyou saw outer space more as a means of extending their reign of power— this would especially be the case if they are surrounded by easily habitable planets. Imagine if the inner solar system looked like this:
Our space programs would not have had any reason to take so much time to colonize other worlds all because Luna, Venus, and Mars are already habitable. The biggest factor in colonization is being able to sustain an imported population with as few imported resources as possible. Compare the colonization of the Americas to the "colonization" of Antarctica. We could grow crops just about anywhere in the Americas, and we even had help from the Natives (when we weren't trying to kill them). They didn't need resources from Europe or Africa. As soon as they learned how to grow crops in the new soil and even receive substantial help doing so, they could eventually go on to create the wealthiest, most powerful country in human history (as of 21/11/2017).
Now imagine that every scientist in Antarctica was permanently cut off from any outside aid. They'd soon resort to cannibalism before starving to death, forgotten by all time. There's absolutely no way to sustain even a small human population in Antarctica. You could possibly hunt some of the native animals, but there's not much in the way of nutrition since the animals there are already somewhat nutrient deprived compared to those from more temperate (or even subpolar) climates.
An alien civilization lucky enough to basically have the interplanetary equivalent of the Americas or even Australia would have set up a permanent colony on another planet circa 1975 in our timeline because it would be as easy as sending a vanguard party and having them figure out how to grow crops. So they wouldn't need food or water flown in, meaning that their space programs could essentially be only a tenth to a hundredth in size compared to how expensive they'd be if they were colonizing dead worlds (in other words, about how expensive they currently are for us). They'd only need to worry about alien viruses and bacteria on that world.
And you want to know the fuckest thing of all?
We're STILL lucky.
Surely most on this forum have heard that restoring Mars's magnetosphere will take technology that we've had for decades and this would kickstart terraformation to the point that humans could theoretically stand on the surface of Mars with minimal protection within a single generation if we had the will and funding. Venus is a lost cause, but Luna is pretty much just Earth with sunbleached dirt— get a stable domed environment and we could grow crops there without much assistance— while Mars is basically a glorified supersized Atacama Desert that is damn close to already being fully Earthlike. It would take very little to tip it back towards being a second Earth.
So while it's exponentially more expensive to leave Earth for good, it can still be done. Maybe if it were the 23rd century and we still haven't set foot on Mars, I'd buy the idea that we're utterly doomed as a species for not caring about space exploration, but I think most in the sci-tech community severely overestimate how important scientific advancement for its own sake is for the majority of the population (including policy makers)— if there's nothing immediately useful, why bother going there? We colonized the Americas trying to find a faster route to India, and we stayed because of the sheer abundance of resources that were there. Sending humans to Mars with no payoff whatsoever except the glory of doing it doesn't entice most people. Whereas sending humans to a Mars that's Earth 2.0 does sound enticing because we immediately start thinking of the possible resources that may be there, or how many people we could support there, or whatnot. And it wouldn't cost anywhere near as much at that, so people wouldn't think of it as a waste of money. I mean, people thought colonizing the Americas was a waste of money at one point. They had more than enough arable land in the Old World— why bother with this new one if it costs so much to go there?
A completely unlucky civilization wouldn't even have that. Their planetary satellite might have far too little gravity or maybe it has arsenic soil... or maybe they don't have a satellite at all. And their fellow rocky planets, if they have any of those either, might be like Venus or Mercury or Europa— if not completely tidally locked, then absolute utter fiery/icy hellholes that can only be terraformed with the technology of a Type 1.5 civilization.
It would still be possible, but it would take even more money and much longer time. With no tangible "bases" they could use to act as stepping stones to launch themselves deeper into space (perhaps they'd have to go the distance of Earth to Neptune just to step foot on a rocky world in their star system), the population might come to believe that exploring space is a completely impossible task and stop dreaming altogether (they may be the ones more focused on oceanic exploration). Whereas for us, we keep dreaming and pursuing that dream knowing that it really can come true (which means we're actually the most frustrated of the lot, but the payoff when we actually do make it will be extraordinary), and for the lucky ones, the dream's been a reality for decades.
So to be awfully honest, we've only had spacefaring technology for about 70 years (I believe the first animals to enter space were a pair of fruit flies in 1947?), and humans have only been in space for 55 of those 70, yet we act like we've been at this for hundreds of years.
As I've been saying for years, it's possible that we genuinely can't colonize other worlds without more mature versions of technologies we're developing right now, like 3D printing. We can certainly go there— we had plans to go to Mars in the 1980s— but without dedicating trillions towards space exploration (which, despite the glorious sounding nature of that, is actually impractical for any government at the moment), we couldn't stay there.