Vuetify + Vue Cli 3 using css variables in IE11?

Question

webpack

Hello toasters!
I wrote down here means an application on vue + vuetify, and in vuetify, as you know, css variables are used, which the god-like IE11 on which I need to start the application does not support at all.
So the configuration is:

package.json

// package.json

"devDependencies": {
    "@babel/preset-env": "^7.6.3",
    "@vue/cli-plugin-babel": "^3.7.0",
    "@vue/cli-plugin-eslint": "^3.7.0",
    "@vue/cli-service": "^3.7.0",
    "@vue/eslint-config-prettier": "^4.0.1",
    "babel-eslint": "^10.0.1",
    "eslint": "^5.16.0",
    "eslint-plugin-vue": "^5.0.0",
    "node-sass": "^4.9.0",
    "postcss-custom-properties": "^9.0.2",
    "prettier": "^1.13.7",
    "sass-loader": "^7.1.0",
    "stylelint": "^9.3.0",
    "stylelint-config-sass-guidelines": "^5.0.0",
    "stylelint-order": "^0.8.0",
    "stylelint-scss": "^3.1.3",
    "stylus": "^0.54.5",
    "stylus-loader": "^3.0.1",
    "vue-cli-plugin-pug": "^1.0.7",
    "vue-cli-plugin-vuetify": "^0.5.0",
    "vue-cli-plugin-webpack-bundle-analyzer": "^1.4.0",
    "vue-template-compiler": "^2.5.21",
    "vuetify-loader": "^1.0.5"
}

postcss.config.js

// postcss.config.js

module.exports = {
  plugins: {
    autoprefixer: {},
    'postcss-custom-properties': {}
  }
};

In theory, everything should work, but in the end, css variables remain.
Styles are written in Scss, they are in the src/assets/scss folder, they are connected:

// main.js

import './assets/scss/main.scss';

Vuetify version is 1.5.5, I will soon move to 2.x.x, if this problem is already fixed / fixed easier in the new version, then I will move the move to the near future.
UPD: as far as I understand, postcss works, as prefixes are added to css, but css variables do not work. I suspect that this is because the variables are defined in vuetify, and therefore postcss does not see them, although vuetify styles are imported in the same way as main.scssinmain.js