Accessibility overlays claim they can fix your accessibility issues and make your site compliant, with only the simple step of running their scripts. No lengthy development cycle needed (and perhaps pay them a substantial amount of money too).
The problem is, they probably won't resolve your issues You're still likely to face legal challenges, and some overlays might even lead to data protection issues, potentially resulting in further legal action!
Hypocrisy
Automated tools can only detect and fix up to 30% of accessibility issues using automated tools.
This implies that to ensure your sites are as accessible as possible, some manual work is unavoidable. While there are numerous extensions, websites, and apps available for testing accessibility issues, none come close to what you need for achieving a reasonable level of accessible practice.
The goal of accessibility overlays is to bypass the need for genuine development work by loading a JavaScript widget onto your site, providing supposed 'accessibility features.' While some of these features might be helpful and accessible, a JavaScript widget cannot guarantee 100% accessibility for one simple reason:
If a user has JavaScript turned off or the script fails to load due to a network issue, causing the widget to fail to load, the so-called 'accessibility features' do not exist at all. Addressing accessibility problems requires fixing the problematic code, and there is no way around this fact.
Even the European Comission advises users against using overlays.
There's ample information available about overlays for you to form your own opinion. Ask yourself, "should I use an accessibility overlay?". If your answer is yes, please reconsider.