Keep in mind, this is only one area of accessibility. Neurodiverse users, users with cognitive issues, users that have a hard time using a mouse, low vision users and even deaf users all have specific issues.

Simply testing with a screen reader is missing entire groups of users.

+1 on this one... I've mentioned it a few times in these threads already... but for the love of all that is holy, try your mobile website/app in an actual phone where you have accessibility turned up for text and display.

I cannot tell you how many times I've experienced modals with buttons literally off screen and no navigation option in apps from multi-billion and trillion dollar tech companies. Almost as bad is gmail allowing text to scale so insanely large that it's equally unusable.