It's very tempting to hand over responsibility over accessibility to other people. If you're a developer, it's the designer's job. If you're the designer, the developer needs to implement accessibility. If you're the product owner, it's the tester's job to make sure everything works with assistive technology.
This is easy. Because if someone else accepts responsibility, then we're off the hook.
I see two problems with this:
1. Someone else must always be willing to accept the responsibility
In reality, this often leads to a situation where everyone assumes someone else is handling it, and accessibility falls through the cracks. When you don't take clear ownership, it becomes an afterthought or gets deprioritised until it's too late. Accessibility requires a shared commitment from the entire team throughout the product lifecycle.
2. You can't really pass responsibility for accessibility around
Accessibility isn't a single task that you can neatly hand off. It's a core aspect of inclusive design that touches every part of the user experience. From conceiving the initial requirements to designing intuitive interfaces to writing semantic code. Trying to tack it on at the end usually creates lots of rework and leads to frustration and added costs.
A much better solution is to willingly take responsibility. Here's the catch though. We cannot simply accept responsibility for our own small slice of the issue.
In other words, if you're the designer, you can't just be responsible for colour contrast and then wash your hands of the whole thing after you hand it off to the developer. If you're a developer, you can't write the code to spec and not care about how it really works with assistive technology.
You're a team, in the same boat and you will all go down with it, no matter where and when the holes appear. So better to work together to reinforce the boat lining and then plug any holes as soon as you see them, without throwing blame around.