Accessibility gets treated as a compliance chore bolted on at the end. Designed in from the beginning it costs almost nothing, and it consistently produces better interfaces for everyone.
The four things that fix most of it
Contrast. Text needs a 4.5:1 ratio against its background. Light grey placeholder text on white fails, and it fails for everyone reading on a phone in sunlight — not only users with low vision.
Keyboard navigation. Every interactive element must be reachable by Tab and operable by Enter or Space, with a visible focus indicator. Try navigating your own product without a mouse. Most teams find something broken within a minute.
Labels. Every input needs a real, associated label — not a placeholder. Placeholders vanish when typing begins and are not announced reliably by screen readers.
Semantic HTML. A <button> is focusable, keyboard-operable and announced correctly. A <div> with an onClick is none of those things. Use the right element and most of the work disappears.
Why it is worth doing regardless of compliance
Accessible markup is better for search engines, which read pages the way a screen reader does. Keyboard navigation makes power users faster. Good contrast helps anyone outdoors. Clear labels reduce form abandonment. There is no group this makes things worse for.
Start here
Run axe DevTools on your most important page. It will find the mechanical issues in seconds. Then unplug your mouse and try to complete your primary user journey. That test finds what automation cannot.