通过从defaultConfig.plugins数组中过滤出原始MiniCssExtractPlugin来删除它。一种方法是在添加修改后的版本之前使用Array.filter（）方法从数组中删除插件的任何示例。

const defaultConfig = require('@wordpress/scripts/config/webpack.config');
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

const config = {
  ...defaultConfig,
  plugins: defaultConfig.plugins.filter((plugin) => {
    return !(plugin instanceof MiniCssExtractPlugin);
  }),
  module: {
    ...defaultConfig.module,
    rules: [
      ...defaultConfig.module.rules,
      {
        test: /\.css$/,
        use: [MiniCssExtractPlugin.loader, 'css-loader'],
      },
    ],
  },
  plugins: [
    new MiniCssExtractPlugin({
      filename: 'css/[name].css',
      ignoreOrder: false,
    }),
  ],
};

module.exports = config;

费萨尔的回答给了我正确的方向，所以下面是我最终得到的代码，看起来很有效。

const defaultConfig = require("@wordpress/scripts/config/webpack.config");
const MiniCssExtractPlugin = require("mini-css-extract-plugin");

//Remove default MiniCssExtractPlugin settings
defaultConfig.plugins = defaultConfig.plugins.filter((plugin) => {
  return !(plugin instanceof MiniCssExtractPlugin);
});

module.exports = {
  ...defaultConfig,
  plugins: [
    ...defaultConfig.plugins,
    new MiniCssExtractPlugin({
      filename: "css/[name].css",
      ignoreOrder: false,
    }),
  ],
};