That is the basis of marxism in a nutshell. It is a scientific framework to observe society and derive conclusions. it is not a set in stone fixed ideology. All real existing socialist projects were and are quite different in practice. And there is a ton of disagreements among leftists about the details. The fundamental common idea is just to create a society that works in the interest of the 99% instead of being controlled by a small capitalist class. How to go about this in detail must change over time since society and the world around us changes all the time. But policies must always be derived from empirical data and the scientific process.

Right now most policies in capitalist countries are created through a very chaotic and mostly unguided process involving competing capitalist interests and the occasional opposing social movements.

Nobody is saying all answers have been discovered, you're confusing political philosophy as a world outlook with a particular formula and set of definite conditions. These aren't the same thing at all, Marxism-Leninism argues against set formula.