Several companies have bought into the idea that accessibility widgets such as overlays are their saving grace when in fact, overlays do more harm than good. In addition to this, the EU and IAAP have released a joint statement pointing out that overlays don't guarantee compliance. According to Usablenet's year-end report, companies using widgets ( a.k.a overlays ) received 575 lawsuits which is a 36% jump over last year. If your company uses an overlay to "fix" accessibility issues with your product, I invite you to read https://overlayfactsheet.com and reconsider. Haben Girma, a Deaf Blind lawyer, released a video asking companies to avoid them as well.
The best solution is to perform an accessibility audit and update any accessibility issues found. Speaking as a Front-end Engineer and certified accessibility professional, I understand the challenges teams face when updating legacy code. I've been there. In fact, that space is where I spend most of my time. So in that same light, as an engineer, I know it's not impossible. It takes time, but it's not impossible. All we have to do is right bad code.