I don't see how replacing uses of classes with selection by id is an improvement - it achieves the same result, but now that "class" can only be used in one place - might as well have used inline styles if css classes are "so bad". Also, you now can't make partial styles, or styles that are only _slightly_ different, eg

textarea { color: red; }

textarea.disabled { color: gray; }

Aiming for full semantic html and applying styles at the tag level _is_ good, but this seems like a not-very-useful refactor which has only made the code more rigid /2c