Variety is important in nutrition. It will not be possible to fit all the substances necessary for a person into the ready-made mixture, there will certainly be a deficiency of some cobalt, magnesium or even fiber. There are substances that cannot be combined in one jar, the simplest example is vitamins B1 and B6: they destroy each other. So, if you make such mixtures, then different compositions for breakfast, lunch and dinner. Judging by the fact that even the richest countries still do not feed such mixtures in prisons, in the army and in hospitals, but continue to struggle with cooking, these mixtures still cannot be eaten all the time.
There are such mixtures. The most famous is called Soylent. However, if we want the mixture to really satisfy all the needs, then it must be prepared individually for each on the basis of an extensive analysis of the body. This will undoubtedly exist in the future.