I think the heart of the problem may be that, like many technical tradesmen, you are talking uphill.
Which is to say; if Seiji Ozawas says he needs the violin section to bow up on the fingerboard during the opening of the Third Movement, everyone accepts that he probably knows what he is doing. But if a roadie says he needs to put a microphone in a particular place on the floor, it is a hell of a lot easier for some middle manager to "Make a decision" and axe that choice.
As a theatrical sound designer, you are more often than not thought of as another part of the running crew. When a Director, Producer, or even Music Director, or even an Equity cast member talks to you, it is always in the back of their mind that they make a hell of a lot more than you do, and stand a hell of a lot closer to the head honchos of the theater when the boozing and glad-handing is going on.
And that can't help leaking into their thinking; that your "opinions" hold less weight than theirs.
This is why there is nothing on this Earth that will cause any of those managers to suspect their own Dunning-Kruger syndrome. And it means there is no possible way to reach across the breach to them. They may intellectually accept that there are technical aspects about sound that they don't understand, but it is far too easy for them to rationalize this into handy compartments; that you as a sound designer understand "what the knobs do" but things like whether it matters where a microphone is placed or how loud the keyboardist turns their amp fall within the domain of things that they are perfectly capable of having a superior understanding to yours.
I just spent three days of bullshit with multiple people yelling at me to "turn the band up" -- and not one of them thought of actually listening for a moment and realizing the problem was that three quarters of the band was tacet for that section and there was nothing to turn up. The Music Director finally had to explain this to them. Fat chance there will ever be an apology to me, though!
I had these same intelligent ears sitting back by FOH trying to micro-manage my mix. This is for a multi-bus mix on multiple speakers, where each major element of the sound environment has a different volume profile over distance (aka stage noise falls off nearly inverse-square, voices are more directional and fall of slower, and the orchestra is in pit but is boosted in the monitors, front fills, and turned down in the delays.)
The only way to stop them from forcing me to ruin the sound for the majority of the audience was to electronically lock out half the Meyer sound system, leaving only the mains still in circuit. That way the front rows are getting blasted, but the difference between the sources is more-or-less smoothed out by the time you get all the way back to the rear of the house.
Oh, yeah. I've tried over the years to come up with a simple example to break through that mistaken paradigm. You wouldn't quibble over the pitch of a note with someone who had perfect pitch. But people seem perfectly comfortable with pointing at one speaker that is part of a finely tuned array and saying "That speaker over there isn't on." (Usually within the context of demanding it be "turned on" because in their untrained opinion it will make the mix sound better.) The idea that sound is a set of skills that includes perceptual skills the untrained person lacks is completely foreign territory.
Why can't they recognize this? Why can they never credit it? Sure, I've wasted time thinking of analogies -- optical illusions, say. Or the way that physics violates common sense all the time. That doesn't make physics wrong, it just makes common sense incomplete. The realms of quantum scale and relativistic velocities are quite outside any common-sense experience.
But I am convinced this is not useful. The problem is not a lack of realization that there are elements in how sound behaves in an environment that go against common expectation, and that sound is everything about psycho-acoustics; about perception being fooled by physics. The problem, I am convinced, starts in a more basic place; with the willingness to admit that there might be domain knowledge.
And worse, that the realities contained within that specialist domain have real-world implications that can not simply be waved away on the basis of "My common sense says it will work, so I'll just order the poor sound guy to do what I think works."
I've had producers ask if putting two mics on the same performer will give better gain before feedback. I've had a keyboard player (a keyboard player!) ask for a cable with USB-B connectors at both ends (so they could plug two slave devices into each other, obviously, which would be perfectly happy without a host involved, right?)
And just this last show, I had -- not a question, I had an order to double-condom a body-pack transmitter because "it is getting wet and that's why it is feeding back."
Not in the physics of this or any other universe. This is the point where you just back away slowly, because there is no point at even attempting to explain.
Welcome to my world.