Not all of our users will have the same abilities that we assume. There are several ways we can improve our product interface to make it accessible to more users. These are considered best practices and usually do not require a lot of time and effort.
Do not prevent users from zooming a page in and out on a mobile device, this is an accessibility issue.
We must determine an appropriate color contrast ratio to match accessibility standards (generally any ratio less than 3 is considered too low). People with low vision and color-blindness are especially succeptible to this error.
The Chrome Accessibility audit tools can be installed in the developer tool panel and will help identify color contrast issues among many other things.
Every image should contain an alt text for visually impaired users that are utilizing a screen reader. Aria labels are only necessary when an interface element has a behavior that is somehow unexpected or different from the normal semantic HTML meaning. Like if a div tag is used to create a dropdown selector instead of using the normal form element.
To get started analyzing the accessibility of any website you can add the tota11y bookmarklet to your browser.
To further assess the accessibility of a particular site I suggest using a screen reader - like VoiceOver - application to experience the website as a unsighted person would.