element.replaceWith(replacement) is just an alias for element.parentNode.replaceChild(element, replacement) with some bonus functionality to convert strings to DOM text nodes. parentNode.replaceChild is not exactly a 'hacky' alternative.

Here it is in the form of a basic polyfill that only supports Elements:

    Element.prototype.replaceWith = function(replacement) {
        if (typeof replacement === "string") {
            replacement = this.ownerDocument.createTextNode(replacement);
        }
        this.parentNode.replaceChild(this, replacement);
    }