If you're after meaningful change, do these three things.
One. Add one accessibility checkpoint to your definition of done. Just one. "Interactive elements must be keyboard accessible." That's it. It takes five minutes to add and your team already knows how to test it. And if they don't, it's easy. Just use your pinky to hit the Tab key.
Two. In your next sprint planning, ask one question: "Who do we think might not be able to use this?" Not "is this accessible" because that sounds like extra work. Just "could we be preventing anyone from using this?" It reframes the conversation.
Three. When you review work, point out one accessible thing someone did well. "Nice work on those form labels!" That takes three seconds and costs nothing.
Three simple things you can start doing tomorrow that will add up to meaningful change.
Then there's things that'll likely take you longer.
Maybe you have a component library. Maybe you don't and need one. Make sure you build accessibility into it over the next quarter or two. Each sprint, focus on making one component properly accessible. Start with buttons this sprint, then move to form inputs next sprint.
Add basic accessibility testing to your CI/CD pipeline. You can catch lots of obvious stuff automatically before it hits production.
Allocate 10% of sprint capacity to reducing accessibility debt. Same way you handle tech debt. Because that's what this is. Debt that'll cost you more later if you ignore it now.
None of this, not even the long term stuff, requires new budget.
You just need to decide it matters.