If I were you, I'd just...
Everyone's got accessibility advice that starts with that. And then they go on and lay out some perfect solution that worked brilliantly in their completely different situation.
Cool story! But you're not me!
You don't have my fifteen-year-old code base held together with hope and RegEx. You're not a one-man team supporting accessibility in five products. You don't answer to my higher-ups who think accessibility is a nice-to-have. You don't have my budget, my timeline or my technical constraints.
But sure, you can tell me I should "just rewrite everything in React" or "get executive buy-in first."
Why didn't I think of that!?
I have a better approach.
Share what worked for you in your specific context, then let me decide if and what applies to me. "Here's what we did with our design system and how it helped." This is actually useful. I can draw my own conclusions. I can learn what I need to. I can pick out what applies in my situation.
"You should obviously do this or that" is just arrogance disguised as knowledge.
Accessibility principles are universal, sure. But implementation is messy, contextual and full of trade-offs. What works for your enterprise doesn't work for my startup. What works with your big team doesn't scale to my small one.
We need to stop telling people what they should do. It's better to share our experience and let them figure out what fits.
And be there to guide them when they have questions.