As someone with a Libra Mars I cannot disagree. I can be very passive aggressive at times. However, I am still successful. I don't think a poor Mars placement makes someone unsuccessful. To your point. I actually met with an Astrologer yesterday with 37 years experience and he said regarding my boyfriend's Mars in Cancer: "they have a saying about Mars in Cancer, they will whine their way to the top." If that doesn't sum up my bf's Mars and how he manages to react to things then I don't know. He may have the most wet blanket of all Mars signs but he is a gifted athlete (Mars is in his 5th house) and he is determined to succeed. I mean we both have "bad" Mars by definition - our aggression comes out wrong and indirect. We both have Mars / Pluto contacts also btw.
I don't think there is anything wrong with saying that certain signs don't behave appropriately when placed in certain signs or houses.
EDIT: I did also want to add that after reading the rest that I think the difference between our Mars signs and maybe an Aries or Capricorn Mars is that Cancer and Libra can be inconsistent. We don't keep the same drive to succeed as those two signs - in general whether it is Mars or any other planet.
Thing is, a lot of people mistakenly look to astrology to find some sort of confidence in themselves, as if their chart reflects good things that they can say they can feel good about themselves. There are more ways in astrology to find bad news than there is good. But not uncommon that are there loopholes to mitigate debilities, there are also loopholes to mar essential dignities. That's just how astrology is, it's a series of vast and seemingly endless layers to peel back and see what other information there are.
As for corrupted Mars, there's actually few "wrong" Mars signs to have. The obvious ones are fallen Cancer, and detriment Libra and Taurus. The strange thing that I always find is that when discussing Mars, Cancer and Libra take the cake as far how corrupted Mars can be. Taurus is corrupted too... but the corruption of Taurus vastly defers from that of Cancer which is uber soggy and Libra which is duplicitous to make any real stance. Both Libra and Cancer are indirect by nature. Taurus is the most solid of Earth signs, and are not soggy at all. Taurus is also not duplicitous and when they make a stance, they stick by it until the very end (for better or worse). Taurus is actually very direct and sure. So what's the detriment of Taurus? The extremity is their demise- and very much like Scorpio, Taurus is extremely black and white. Either Taurus is completely off, or completely on. There's no middle ground. When they're on, they're on full force until the whole house collapses. When they're off, the whole house can deteriorate. Taurus isn't a light switch to be turned on and off so easily, rather it's like crazy glue and you have to be careful where you apply such dangerous substances. Libra is like Goo be gone spray- to undo crazy glue and other sticky substances; remove all attachments. Cancer would be like the defective sticker that could not stick and gets resent back to the factory to be replaced
This topic is originally about the Moon so I'll go back to it.
The Moon is very sensitive and dislikes being in most signs. Aside from the Moon being unhappy in its fallen of Scorpio and detriment Cap, the Moon is also not happy in Gemini as that's the 12th house from her domicile, and next to exalted Taurus (signs next to each other don't "see" or "interact" with each other), nor any Fire sign because of their difficult placement in relation to domicile and exaltation. Moon is not happy in Libra as Libra is also inconjunct and square to Taurus and Cancer. Moon has difficulties expressing in Aqua as that's inconjunct to Cancer and square to Taurus. Already I axed out Moon in Fire and Air signs. 1 Water Moon is fallen, 1 Earth moon is detriment. The only Moons left are Virgo and Pisces which trine and sextile to domicile and exaltation. So out of the general equation, there are only 4 "right" Moons which are Taurus, Cancer, Pisces, Virgo. Moon is, after all, extremely sensitive.
Now the catch is, just because a person has a "right" Moon or any right planet, it doesn't mean it makes the person well-equipped for life. For one, Water Moons in general are entrenched in...well, Water and the one that has the most vast, endless body of water is Pisces. Having Pisces Moon makes it difficult to handle all the harsh aspects in life, and life is harsh at every turn. The way that Pisces Moon tends to keep real life at arm's length and retreat to their own brand of fantasy for comfort...which makes it easy to be dependent on drugs, get involved in abusive and co-dependent relationships, and other various self-destructive activities.
And when such a person has the right Moon, but it being placed in a malefic house such as the 6th, 8th, and 12th (all houses inconjunct to 1st house/Asc), the Moon can easily lose her way because she's not able to communicate to the strongest house (the 1st). I have such a Moon... in the right sign but wrong house and with very wrong aspects to every other planet which adds difficulties to me. Someone with the wrong Moon such as Aries can have it in the right house such as the 1st and they will rage against the world and have their way all day, everyday. Because they have no qualms or any awareness of how aggressive and overbearing they are, they can actually be a lot more "successful" than someone with the right Moon who is so sensitively and painfully aware to not be a pain in the @ss.