Bismillahi rahmani raheem, assalamu alaikum
The answer to what ruined Jinn in our time is very simple, but to reach it and see that is what occurred is not, you need a deep understanding of the heart, fate and the spiritual world.
As man lives his life each time he experiences something he forms an opinion and feeling about it in his heart, today these are seen as very cheap things, how you feel about something comes and goes, but the reality is that is the gold (Dhahab) of the spiritual world around which it revolves, even the Arsh of Allah, His throne revolves around what occurs to man’s heart.
The same is true for Allah’s other creatures, His Angels and Jinn, what ends up in your heart is also your spiritual connection to the rest of the universe, it decides your fate, Karma, how the universe will react to you based on what you experienced and what reached your heart.
There is a saying among the scholars and Awliyah (saints), “Qalb al Insan Arsh al Rahman”, the heart of Man is the throne of Allah (by which the universe is moved), what we are discussing is the meaning of that understanding they witnessed about man.
They witnessed that the entire affair was cause and effect, If you experienced oppression that feeling in your heart will make the universe react to what you deserve as a result, that may sound like I am making this big but in fact physics explains it very simply, what is in your heart is a created from particles, even your feelings and memories, and particles can entangle themselves with everything in the universe no matter how far and connect you to it, it is called quantum entanglement and your experiences as you live them make those connections and give direction to that entanglement.
What I just explained is an old understanding given a modern context in science, so understand this is what the scholars understood without the science of how.
But if Karma, what you deserve as a result of your suffering or hard work is cause and effect and not something magical and uneducated, then somethings can interfere with that cause and effect and change what you deserve as a result.
The reason Allah made music Haram, more specifically stringed and wind instruments like the flute, violin, saxophone and piano is because it emptied the heart of everything it earned spiritually from your years of living.
Music can make you cry, laugh, ecstatic it can make you live out an entire life in a single song, but once you live it you have lost what your heart had, all those years it took to get there, and that is the key to understanding all of this.
Because of one song you have lost years from your life, you have lost your spiritual connection to the wealth you earned over a lifetime while you listened and cried. You have ruined the Mizan/balance of your heart, so it is like being robbed of your worth, imagine not being able to love your wife like you used to love her because of a song.
Music was the original medium that did this to man and Jinn, but today we have television, movies and video games that all do the same thing and this matter is worse for Jinn.
They can live out an entire life watching a single tv show and for them that is complete Maskh (stunting of their spiritual growth), they can no longer develop into proper adults and as a result they can no longer help man develop into the same, which has been their job with man from the time Adam (ra) came to this earth.
Man showed Jinn how to stand up and Jinn helped the next generation of man reach the same, this has been our co-existence with them and the prophet Muhammad (saws) called Muslim Jinn our brothers in religion because they looked after us.
Today most Jinn are ruined because of Music, television, movies and video games, they are increasingly immature and as a result increasingly devilish, but their level of immaturity is self-assured destruction, they will bring an end to you and themselves without a care.
The word Majnun/insane in Arabic comes from the word Jinn because of how insane they can act and make others act.
Imagine how much entertainment there is in the world that is how much the hearts of Jinn and mankind are being emptied of their wealth every day, that is why we are all spiritually poor.
Shaykh Rami Al Rifai.