I have also wondered about this when boycotting companies for reasons that I suspected were not the most common reasons.
If they sent out a survey about "why you're no longer a customer" I suppose it would provide one channel for explaining one's actions. Oddly, I seem to get those constantly when I am a customer, but essentially never when I'm a former or inactive customer.
On privacy grounds I like the idea that non-customers would be left alone, but on boycott-impact grounds it seems like having some kind of predictable "what are we doing wrong?" channel would be nice too.
Thus the thing to do, for funsies, is to subscribe, and then cancel, and give the poor customer service person on the other end of the line, a piece of your mind, every time you cancel. Boycotts generally don't work. But the goal is to make a signal that gets noticed by the C-suite. Unfortunately, the routes I see are in the pocketbook, the customer service department, and via Twitter, if they do actually happen to be there. A sustained prolonged boycott would work, but most people don't care. Screaming at the customer support person is just shitty to a low level employee that doesn't have the ability to affect change so empathetically thats horrible to do to them, so that's a no go as well. But that is by design. Thus, one way is to overcome that and be horrible to the CSR. But that sucks.
Yay, American "capitalism".
Being horrible to the CSR will never be noticed by the C-suite.
If you think they give one flying fuck about what customers think I have news for you: the only thing that matters is what the board thinks and if revenue is rising but everyone hates the product/company they won’t even blink.
Even then, it's a share price that matters to them. Revenue affects that, but unless they get a K1, it's the share price that really matters.