large part of it is
sociopolitical: major populated and productive countries are locked by their social and economical structure into the need of perpetual growth to inject capital at the base as the top scoop up any floating wealth, stopping the growth without some for. of wealth redistribution would cause massive instability and with the margin of today production the first two to introduce climate control will be eaten (economically speaking) by the third one.
on the other hand we could likely today engineer algae or fungi to fix carbon into cellulose but you're going to need massive space for their growth and some place for their disposal, unless you can make some sort of bioplastic out of it, because burning them would defeat the purpose, and I bet once you put the number in the unbelievable scale needed for the project would scare the bejesus out of the very same ambientalists types that are currently most vocal about saving the world but abhor nuclear
anyway I think the real issue NASA has about bioengineering are ethical, and Venus is in the same protection category as Venus https://en.m.wikipedia.org/wiki/Planetary_protection
you can draw parallels between the development of cities as Rome, London, Chicago and Los Angeles substituting environmental protection with historical buildings protections. it's important to preserve the best and most relevant landmarks of course but too much and it becomes a real drag.