Errikos, you noticed of course that in the OP I kept away from certain (mostly speculative) causes and effects. That's largely because it was already getting too long and I didn't want to try encompassing too many topics at once. But I would certainly accept the criticism that the OP is thereby somewhat lacking in foundation, and if so, you have my unreserved apologies for that.
You've identified a highly pertinent issue:- how big or small a factor is ET v OI in so much of today's lamentable excuses for "composition"? In my opinion it's a huge factor. It's not hard to observe that people tend to get lazy and slipshod in their speaking and writing wherever slang and dumbed-down idioms are the norms - e.g. in Twitter and so many other online platforms. In my opinion, ET has had a very similar bad influence on all too many of today's writers of music - both serious and pop.
The "pidgin" I mentioned has long been for me a telltale sign that the music's writer has come to believe (or perhaps has always believed) that ET is sufficient unto itself - nuance, subtle inflection and tantalising glimpses of profound insight be damned. Henry Miller's books outsold the works of Shakespeare and Goethe put together and that's all that matters, right? I believe that focusing only on using ET as the basis of the language of music has necessarily robbed all too many of its users of the breadth, depth, richness and nuances of expression that OI has furnished for many centuries. And so it's hardly surprising to find that aesthetic taste in music is disturbingly thin on the ground these days.
Worse, I fear that ET has been and is increasingly being used as a cover or disguise by those phoneys who have nowhere near the strength, integrity, depth and sensitivity of character needed to write orchestral music as the greats once did, and yet who nevertheless harbour grandiose opinions of their own abilities and talent, and who insist on promoting themselves above others simply because of their grandiose self-image. It's all about stardom and celebrity, right? Fake it till you make it, right? Taken in isolation on its own virtues, ET is as specious and phoney a dissembler as these grandiose toxic wannabes are; hence for them it can be a Machiavellian enabler.
It's also notable how few of the great composers of the past managed to transcend the dire limitations of ET and write sublime, exquisite pieces for pianoforte. What are the chances of a great piano piece being written today that would rival those of Beethoven, Chopin, Debussy, Rachmaninoff, etc? I'd say nil.
If I may throw in one more metaphor, I believe far, far too many would-be composers today have given into the addictive temptations of ET as 'junk food', never mind that artistic taste, 'nutrition' and long-term health all take a serious nose dive as a result.
"Music embodies feeling without forcing it to contend and combine with thought, as it is forced in most arts and especially in the art of words."
~ Franz Liszt