Atmosphere itself is plant technology. It wasn't here before life and it won't be here after. Earth WAS pretty inhospitable, life just overcame those hurdles. Chances are we can do it again. It won't be easy, cheap or quick though.
I don't think you quite understand. Earth's atmosphere existed all along; its composition was just different before plants came into the picture. But even plants need certain atmospheric conditions, such as the existence of an atmosphere and certain elements in it. Now, it's true that the composition of Mars' atmosphere is all wrong even for plants (for example, very little nitrogen), but more fundamental than that, its atmosphere is literally barely there — the gas around the planet is exceptionally thin. Venus, Earth and Mars are like the three bears — Venus has way too much atmosphere to support life as we know it, Mars has way too little, while Earth's is just right.
Venus is hot enough to sterilize anything that even approaches its surface. Earth's most radical extremophiles don't even come close to being able to withstand that. Even life made out of many common metals wouldn't be able to exist because it would melt them.
Since we don't know the limits of what might be considered "life," I suppose we can't 100% say it's impossible, but that's why I said "life as we know it."
There are many materials that melt above 500C, so it gives theoretical possibility for existence of life on Venus.
I couldn't be carbon-based life though.
BTW, Venus civilization would have similar reasons of not going to Earth as our reasons are of not going to Mars: way too cold and not sufficient atmospheric pressure.
