And by 'we've failed to terraform', did you mean 'we haven't tried yet'?
Plus, there's no life that we know of on Venus. A bacterial population capable of living, evolving, and growing exponentially in that environment would be a huge change.
California's Central Valley project is an example, and China has some that are even larger.
Worst case scenario is we'd lose some valuable scientific information about Venus in its natural state.
It seems like a remote risk to me, but not something to shrug off. Particularly since the usefulness of introducing life to Venus is itself quite remote.
Why not? It'd have to have different chemistry, sure, but even on Earth life exists in some pretty extreme temperature and environment ranges.
Life that could operate at 500 C is probably not water based at all, which would be very novel and certainly interesting to science.
To some weird soul out there on the Internet, this sounds like a challenge.
https://en.m.wikipedia.org/wiki/Terraforming_of_Venus
It would probably require more advanced bioengineering and understanding of ecology and extremophiles than we currently have, but it might still be the only feasible plan.
To be clear, I mean if someone drops a bunch of microbes, only once, and not all of them die but slowly start to mix and live in the atmosphere, wouldn't they over millennia, very slowly but also very unstoppably, eat until everything they want to eat is eaten?
Some related links:
https://planetaryprotection.nasa.gov/intpolicy/
I mean yes I do kinda see your point, but priorities man. There are ridiculously large advantages to colonizing the universe and destroying a few samples is a low price.
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.