This video shows a couple of techniques that you can use to maximize alt text and accessibility when rendering text as images.
Breaking the text into smaller chunks (e.g., paragraphs) using the free Split Text extension lets you apply more Alt text within Google-friendly limits.
See also How to Add Alt Text to Images (and Other Page Items) with InDesign.
The Mobile Article Explorer is also a great way to display text for easy reading, while also keeping your pixel-perfect layout.
More techniques like this can be found in the Accessibility & SEO course on Ajar Academy.