There was a period where there was major demand for form widgets in the browser to have a "native look and feel" to decrease the learning curb for people coming

There was a period where there was major demand for form widgets in the browser to have a "native look and feel" to decrease the learning curb for people coming from native apps (while meaningful at the time, is less of an issue when most things are web-deployed), and then like the next month there were demands for CSS styling of form widgets and browsers were being shat on because they only supported it in a limited fashion, only color changes, and not actual shape and text styling. Now you can make text on a button bold italic, but who knows what that means when you see it in relation to a button that isn't bold italic or is just bold or just italic (other than that the designer has bad taste). I once worked with a designer who wanted control over the focus-caret styling (the dotted line in Firefox/highlighting in Chrome that indicates where keyboard input is destined, which changing has potentially huge impacts for accessibility). Having a UI/UX that grossly visually distinct negatively impacts usability, discoverability, and accessibility, IMO, for very little gain in branding (unless your branding is purposely meant to be "confusingly different from everyone else").