Part of the problem here is that there is a
balance to be struck with these sorts of things: Cost, User experience, Mange-ability, and time spent shopping around rather than just going with the industry-default or one with the best sales-team. Responsible decision-makers have to make trade-offs.
When you say
> Reports...are roundly ignored
That lack of weight given to your experience as a signal of real business cost is a real problem.
So what is the solution?
1. Understand the problem they're trying to solve. What are their real motives and pressures?
2. Understand where your needs align with theirs and where they diverge in reality.
3. Tell a compelling story of where your needs are in fact aligned.
3.1) Prepare Evidence
If your case is "This tool is causes literal permanent eye injuries to our staff", then there should be written reports of those injuries. If your case is "This software package has multiple missing-affordances which present operational risks to the business", then you should be able to take screen recordings of that.
3.2) Start with why
When turning evidence into a presentation, remember that people listen better when they know why they are listening. So start with: What is at stake?
3.3) Credible language
If your words say "the UX for hundreds or thousands of others is 'the software literally shoots knives out of the monitor and gouges out your eyes'" but you can't actually back that up with the factual reality, you seem like you're exaggerating. If I think you are exaggerating, then I can't trust your words when I'm trying to understand magnitudes.
If I can't trust your words about magnitudes, then how do I give you a voice in making a well-balanced trade-off?
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Literally: (adverb)
1. In in a way of speaking that is completely accurate and unexaggerated.
2. In in a way of speaking that is exaggerated for emotional effect.