Web games running within Itch have different restrictions, but I recall that the 200MB limit applies to each individual file inside the ZIP.
https://itch.io/docs/creators/html5#zip-file-requirements
The ZIP file should not contain more than 1,000 individual files after extraction.
The maximum length of a file name including path should not be greater than 240 characters long.
The size of all the extracted content should not be greater than 500MB.
The size any single extracted file should not be greater than 200MB.
The filenames are case sensitive and should be encoded as UTF-8
If you can’t reduce the file size, one option is to offer the full version exclusively as a downloadable game—even if it’s built using HTML. I’ve seen several games created with Twine that do this.
You could also provide a limited demo version that runs online via Itch.
This way, people can try the game online, and if they like it, they can download the full version.