I am not a big fan of rules in astrology, but of course they do exist. To say that planet A in sign B = effect C though is overly deterministic. I would say that very often, people who read their own charts, the same as people who read their own tarot are going to be prone to reaching the conclusions that suit their subjective deductions.
Personally, I look at my own astrology in a fairly abstract way, if I want a properly objective opinion I ask one of the astrologers here who I trust to give me their view, I have asked for help from Gaer, Starlink and EJ53 to name but a few and I have found in all cases that they provided insights to an issue which I really could not see very clearly.
What I will say about Moon in Capricorn is that it works toward stability, toward practical goals that fulfill emotional objectives, that makes sure that the environment is supportive. I honestly cannot say that it is associated with depression unless you perhaps bracket a dry, dour, undemonstrative demeanour into the same diagnostic criteria.
I would say that the Moon does nothing consistently, so if you are consistently unable to find the joy in life then look to Saturn, an afflicted Jupiter, slow and difficult transiting conditions, perhaps by Solar Arc or secondary progression.
In the case cited above, I would consider Neptune in Sagittarius to give a real yearning for the far-off and profoundly prophetic, it diffuses the already expanding domain of Jupiter, so it is a highly contemplative, spiritual and philosophical placement that rising personalises and creates a need to express that very delicate and refined feeling, but in square to Saturn in Virgo, which demands almost the opposite, a fussy, pedantic, nit-picking quality that in the 9th directly contradicts the dreamy expansiveness of Neptune; that creates a real drag on the primary mode of self-expression, weighs down the spirit with self-criticism, creates a struggle between idealism and materialism, and the worrying nature of Saturn would really depress the spirit denoted by Neptune.
And what is depression astrologically? Is it to do with the emotions or the spirit? In my own experience of it, true depression is like an existentialist angst, not a functional, immediate, fluctuation. Now it may be that a Moon placement at 14 degrees Capricorn may incline to suicidal thoughts, but that is true of any placement at 14 degrees of the Cardinal signs, so it is not unique to Capricorn. Furthermore, I am not ruling out the possibility that Moon in Capricorn can be configured in a case of depression; I am only saing that in my experience, Moon in Capricorn does not incline to depression in the clinical sense.