Also... A LOT of people are becoming more spiritual right now. There's a huge spiritual movement on twitter for one and I don't think it's so safe to think they all have similar chart aspects. It's something that people will pursue for different reasons and there are different reasons people might pursue selfimprovement too. An easy answer is Pisces, but then look at its opposite, Virgo. Virgos can be wholeheartedly devoted to selfimprovement and finding a much needed realm beyond heavy selfcriticism. I personally don't have anything in my 8th, only my Pluto in Scorpio, only a quintile between moon and Pluto, and an empty 12th house with just my moon conjuncting it, but I'm very spiritual. That's why I'm pretty passionate I guess about this topic. You can say Scorpio maybe, but then I've also seen people with lots of Taurus who are extremely spiritual
Astrology itself could be looked at as a window into why's rather than whats in terms of spirituality and many things really. So where someone's NN is in regardless could give much insight into how one approaches spirituality and why. Like for me, I have it in my 4th in Sagittarius and one of the big drives is finding a personal self truth. Finding who I am beneath all the superficialities of humanness
I agree partially with you because I perhaps understood the topic in a different way. Of course all are meant to evolve one way or another, regardless of the chart. However, people with "less spiritual" signs tend to read more into the spirituallity and learn it rather than feel it, have it already in them, aka come into this world with the knowledge. And this all shows the development of the soul imo. Not all can reach nirvana in this life.
Some people with specific placements and signs and aspects tend to be "born this way". Take for example the famous prophet Baba Vanga. Her birth time is unknown but her chart is Uranus dominant.
She has Sun, Moon, Venus in Aquarius, Mars at 29 Sagittarius, Jupiter in Scorpio, Saturn in 0 Taurus, Uranus in Capricorn (I'm lead to believe that capricorn is highly spiritual sign, since it's ruled by the lord of karma, represents status quo, somehow all Capricorns have this inborn understanding of karma and how it works, perhaps because Saturn has used them many times being his hand of karma.)
Now lets look at Nostradamus.
Moon in Scorpio in 8th house.
Uranus in Pisces in 12th. Those two are already powerful enough
Sun conjunct MC, Pluto in Sagittarius in 8th
North Node in 12th
Mohammed:
Jupiter and Saturn in Scorpio 9th H
MC in Scorpio
Aquarius ASC
Pluto opposite Moon
Pluto in Aqua
Sun in 0 Taurus
Now lets take a look at Thomas S. Monson, a famous RELIGIOUS leader. "As president, he was considered by adherents of the religion to be a "prophet, seer, and revelator." Monson's early career was as a manager at the Deseret News, a Utah newspaper owned by the LDS Church. He spent most of his life engaged in various church leadership positions and public service."
We are talking of high positions, public figure, leader mind you, not spirituality.
Sun conjunct Neptune in LEO
Moon conjunct NN in Gemini (known to be quite controlling and a bit power hungry)
Mars and Venus in Virgo , practical sign, perfectionist, controlling
Uranus conjunct Jupiter in Aries ...
This chart shows TO ME at least it was all done in the name of publicity and fame... if he really believed in what he preached is another story.