I honestly think this is a misconception. With enough mental discipline, I actually think Libra is the best at decision making! (Gemini on the other hand changes its mind 1000 times a day) Libra is represented by the scales; Libra is the lawyer, the JUDGE of the zodiac hence why Saturn is exalted there. I don't think Libra is indecisive so much as it is slow to make a decision, because it needs to consider all the evidence. Aries is an action-orientated sign. Aries makes decisions quicker, but quicker doesn't necessarily mean better. Most people make their decisions quickly based on feeling, the impulse of the moment and this isn't always smart. This is how I feel about politics most of the time.
I'm a Libra, and I'd say I get along best Aquarians. Both signs tend to be concerned with humanitarianism and issues of social justice. But out of all signs, I'd say I have the most troubles with Leo, actually, despite the fact that we're generally considered "compatible". Leo is about ego, Libra is about relationship, how can that possibly work out? But a lot of other Libras say they like Leos so I figure it could have something to do with the abundance of Scorpio in my chart. I can't take anyone telling me what to do. I'd say it's similar for you: it probably has something to do with your Capricorn planets. I don't get into as many fights with Capricorn as I do Leo, but I can't say I click with them either. Leo Sun + Capricorn Moon has been the most difficult combination for me to get along with. The thing is Capricorn and Libra are completely opposite in outlook. (In my experience,) Capricorn sees Libra as idealistic and naive while Libra sees Capricorn as close minded and boring.
My Midheaven is at 23 degrees Aquarius loosely trine my Sun at 27 degrees Libra. A 23 degree Libra Sun would be trine with you. I don't see how the degree could have anything to do with it. I would say it's the Venus and Mars. My Sun actually is square your Mars and Venus.
