What most techno-solutionists don't see in their own rhetoric is that, while our technological prowess makes us a lot more capable of tackling those challenges than in the past, the same technological prowess makes us also much less likely to miscalculate the threat that we're under.
Techno-solutionism is a stance held mostly by two groups: (1) highly educated STEM people with a huge conflict of interest to make technology _the_ solution, and (2) poorly educated people who don't want to hear about the problem, and figure that "technology has saved us from diabetes, bacterial infections, polio and so many other threats, this will surely happen again".
The problem here is that the first group has Dunning-Kruger understanding of the global situation, because they are both uninterested in the actual solution and too interested in the non-solution, while the second group doesn't understand shit of what's going on* and doesn't trust anyone anymore.
So, while I am not inclined to say we're doomed, I have to admit that the current dynamics don't play in our favor.
[*] The best clue of that might be that lots of them don't see any contradiction in thinking that technology will save us from whatever comes next, while refusing to vaccinate their kids against the disease with the most awful lethality/preventability ratio: tetanus.
Problem is: those resource limits are essentially fixed. There's only so much greenhouses gasses we can put in the atmosphere before wreaking havoc on the climate. No technology will give us a 2x or 10x GHG budget. Similar story with energy, minerals, metals & so on.
Technology solutions may come. Or not. But you can't be sure that for any problem x, some tech y will be developed to solve it.
And if it does: all you've done is move the goalposts, and a while later you're back at the same problem. For example the green revolution allowed this world to feed many more mouths. So population exploded, and now we're back to the same problem, except with 8..10 vs. 1..2B mouths to feed.
Techno-optimists lean too much on those technology fixes to appear (and in time!), imho. A more realistic approach is to start with what's currently possible (or what seems realistic near-future). Then if new technology appears, it'll make the problem easier. Just don't count on it.