Storybook's own styles are overwriting my component styles

Issue link: storybookjs/storybook#16545

Steps to reproduce

1. Clone this repository

   git clone git@github.com:ed-asriyan/storybook-bug-sample.git
   cd storybook-bug-sample

2. Install dependencies

   npm ci

3. Serve the app

   npm run server

4. Open http://localhost:8080. Make sure, that you see this text: if you see this text the .loader element is rendered correctly
5. Run storybook and open App component in it

   npm run storybook

Actual result

There is Storybook's loader inside App component:

The loader has the text inside:

Expected result

if you see this text the .loader element is rendered correctly text is displayed inside App story