Isn’t that so?

li:not(:last-of-type){
}
/**:last-of-type指的是相对父元素的最后一个li元素**/

The answer on the second floor can also be used

li:not(:last-child){
}
/**:last-child指的是li元素而且这个li元素是父元素的最后一个元素**/

/**等同于楼主的**/
li:not(:nth-last-child(1)){
}

What’s the difference between the two?

When the child elements of the ul element are all li elements, the two are the same

<ul>
    <li>
    <li>
    <li><!--第一个和第二个选择器都会忽略这个-->
<ul>

But if not all the child elements of the ul element are li and the last element is not li either

<ul>
    <li>
    <li>
    <p>
    <li> <!--这时候第一个选择器会忽略这个,而第二个选择器会全选上-->
    <i>
<ul>

li:not(:last-child){
}