One problem, as I see it, is the number of "scientists" with different scientific qualifications, such as Flannery has self admitted.
It would be difficult for anyone scientist or politician to prophecy what will happen in 2050.
There will be so many different "expert" and "political" theories that there is a random chance some will be right.
With computer modeling, one decides the outcome required and then writes the program guesstimate parameters to, miracle of miracles, come up with exactly the desired result.
I recall, about 40 years ago that "scientists" claimed that the Great Barrier Reef would be dead by the turn of the Century. It wasn't.
On the LNP plan for Net Zero, there is an often criticized element of technology "not yet developed". perhaps the critics believe there will be no new technology. Look at the last 29 years where there has been many advancements.
Anyway, even if the plan is flawed, it is better than no plan except being popular now with extravagant claims that will be the next generations achievement problem.
If one takes the life expectancy of 80 years (approx), then any scientist or politician over 50 may not be alive, let alone active in achieving the goal/target/aspriation/whatever.