Scientific theories are based on and lead to repeatable experiments, while pseudo-scientific theories are based on and lead to experiments that are uncontrolled and / or irreversible. These are the two main characteristics of true science: control and repetition.
Controlling means that it is possible both in theory and in practice to eliminate possible factors that could affect the outcome. Because of the many factors that are eliminated, it is easy to claim that only one thing is the real cause of what we see. For example, if a doctor thinks that drinking alcohol makes people healthy, they will give you a test subject, not just alcohol, but a drink that contains only some of the ingredients from the wine - see which topic is good. Most will show that what is in the wine is responsible.
Repeating means we can not be the only ones who come up with our results. In principle, it must be possible for other independent researchers to try to do exactly the same experiments and come to the exact same conclusions. When it happens in practice, our theories and results are further substantiated.
In astrology, however, there is no control or recurrence that seems normal-or sometimes even at all. Controls when they appear are usually loose. When controls are tightened enough to undergo regular scientific scrutiny, it is common for astrologers' abilities to manifest themselves to some degree.
Repetition also does not actually happen, as independent investigators cannot replicate the findings of astrologers. Even other astrologers could not confirm the findings of colleagues, at least when the study was strictly monitored. Thus, as long as the findings of astrology cannot be thoroughly established, astrologers cannot claim that their findings are consistent with the fact that their methods are valid or that astrology is true.
Image Source: https://www.scientificamerican.com/article/is-astrology-real-heres-what-science-says/