I know we do not have a version of QFT (?) in which we can dynamically solve for the QFT and the background spacetime at once. What we can do is where if we come up with a QFT whose expectation value of the stress-energy tensor doesn't match the fixed background spacetime geometry via the Einstein Field Equation, we go back and try again taking or taking *back reaction* into account. The question I’d like to ask is. Is this normal due to simply incomplete QFT tool.. or is it really necessary to quantize spacetime--or at least to build a quantum theory of something whose classical limit looks like spacetime? In our daily life. We think Schroedinger Equation is enough in our biochemistry and we walk visualizing Galilean space. Sometimes we may think of QFT a bit as we navigate in minkowski spacetime. But I want to get used to think in terms of QFT in curved spacetime as this is the more complete mode. Therefore I’d like to know if the backreaction thing described above can exist by its own (meaning can be complete itself) without quantizing spacetime or create something where the classical limit looks like spacetime.