I am a Scrum Master, because I decided that if I can't avoid Agile, at least I might learn to do it properly. So I got some training and read some books. And I was confused, because "this sounds nice, but is totally unlike any Agile I have actually seen as a developer".
Then I took my role, and tried to implement the first thing they taught us at the training... but the management said "no". So I tried a different thing... but the management said "no" again. I asked what's the point of sending me to an Agile training if they override all my decisions, and the answer was, more or less, "we are doing Agile this way". My options were limited to do "Agile" their way, or to quit my role and be replaced by someone who will do "Agile" their way.
So now we are doing Agile the way everyone hates and everyone does, with me in the role of the bad guy. Except our standups are 5 minutes long, because... that's the only part that remained firmly under my control. Otherwise, everything is the opposite of what the Agile trainings and books said. The management made a big announcement where they congratulated themselves for successfully transforming the company to Agile.
From my perspective, this answers the question why "true Agile has never been tried". The people who make the decisions, they want the buzzwords and some of the rituals. They do not really want to give up any of their managing power.
To try the Agile as intended... you would probably have to start a cooperative. Or be a very enlightened founder who can resist the temptation to use their power.