Why do you think we don’t need a more precise idea of ​​the society we want to build first? Without prior mass consensus on the model to be implemented, how can we ensure that it will not end up with a system as bad or worse than the current one?

this a pretty deep point of contention that marxism has with a lot of the western left, for probably a whole litany of reasons. the two most essential i can think of right now are:

• the more expertise anyone (or any human organization) has on a topic, the more knowledge you have regarding how to actually acquire expertise. by contrast, the less expertise you have on a topic, the less you know about how to acquire expertise. this is why teachers are so invaluable, but there is no fully-formed communist society to learn from and so we can assume that we know very little (relative to communists hundreds of years from now) regarding what communism will literally look like. imagine a beginner artist trying to comprehend the practices and technique of a master artist before making concrete steps towards improving and becoming a master artist themselves: it would be a fool's errand.

• the farther things are in the future, the less certain you can be about specific claims or goals. if we are to take the rest of history as a guide, then communism will take hundreds and hundreds of years to successfully develop (possibly more, since resolving all class contradictions just hasn't been done before, so who knows how long it will actually take). even completely ignoring all technological advancement, i don't think anyone from 1000 years ago could have possibly envisioned the basic social relations (wage labor, but also things like globalization) that make up present society.

with those things in mind, the correct approach is then to take specific, concrete steps in the present to move towards general goals in the future. those general goals should be as specific as possible, though, and this is why marxism focuses so heavily on the resolution of the primary internal contradictions of society, i.e. class, as opposed to the overly general goal of "making society more fair" or other such things that are too susceptible to existing class biases. furthermore, it's important to have quantitative (and therefore objectively measurable) measures of success to ensure that progress is actually moving in the correct direction.

as far as the political necessity of models in the present, i don't think there needs to be "prior mass consensus on the model to be implemented" in order to qualitatively change society for the better. the masses are not stupid, but they are largely uneducated as well. most people simply care about their quality of life and whether or not it is improving in the short-term, and there's nothing wrong with that. it just so happens that the best models for long-term social success also provide the best models for how to improve people's quality of life in the short-term, too, so long as they can actually be applied. this will become more and more relevant as conditions in the imperial core get worse and worse.

that's not to say that the question is meaningless or not worth thinking about: i sometimes daydream about what non-patriarchal familial relations will be like and things of the sort. it's just that i recognize it as daydreaming and don't really give it much importance in terms of what should be done now.