hey, the burden of proof is kinda on you. how would it fix it? but sure, I can rant regardless... but not to refute an argument that is just a bald assertion in the first place ^^
yes, now having a terraformed planet and a fleet of transporters would be nice. it would "help". but we don't have that. if we don't fix our situation, we likely never will have, not without murdering billions of people, or just letting them die -- it would suck either way. if we fix it, living off-planet is not required to survive choking on ourselves (which is what is happening), but a nice bonus.
if you move us, like we are, elsewhere, that won't help. it's like when someone doesn't know how to read, that reading it for them doesn't "fix the situation". it's just a crutch. that's what going elsewhere in response to this would be.
and I doubt it's feasible in the next few centuries. you gave no solid arguments to the contrary, so that's the default position. technology has advanced a lot and will make leaps we can't imagine yet, I don't doubt that... you could also say there have NEVER been so many hungry, thirsty and poor people on the planet. it's not just technology, it's logistic, economy, politics... tech gadgets for some, mostly as entertainment, aren't progress. our technology and what we invest in is actually embarrassing, not impressive.
so saying that will just suddenly change, without efforts on our part, or even some uncomfortable changes, is BS. if we don't make effort, why would future generations do? and by the time it impacts us, our choices will be drastically limited. then they'll just chant and say "it will be better in the afterlife", just like we now say it will be better in the future, and fizzle out. that's my worry. not that humans will go extinct, I doubt that, but that we get thrown back a big deal, by our hybris and greed and apathy.