Try to use local apache server for web page index.html, If you trying run game as local web site it could help. For local server you can use XAMPP for example.
We're using Unity and I didn't realize building a webGL game drastically changes how the game is rendered. I usually make games for macOS or Windows. Building out a web version and loading it up in a browser was eye opening for me. The lighting and colors look completely different.
If I try to run it in browser by clicking on the Index.html file, mine does the same thing as yours. But uploading it to my dashboard on this site, it runs fine.
