I mean, it's based on more science than all the alternatives.
Yes, the standards are a lot less rigorous and reproducability is worse than in the "hard sciences", but at least they are trying to get some kind of objective, reproducable result in the first place.
The alternatives to therapy are basically: Religion, family knowledge, random self-help books or trying to work it out yourself. In all three, the methods are even less stringent and objective than in psychology.
In my experience, psychology as a field is also open to new information from biological hard sciences, such as neuroscience.
Finally, note that psychology is not just used in therapy but also in advertising, UX design and tech in general, often in manipulative ways which run counter to the interests of users. Evidently, it works there. So then, why would the same knowledge suddenly be useless pseudoscience when it comes to therapy?