It is there with Office 365 and VS Code live share. They were among the first to make a complete and commercially successful coediting experience.

The webified version of Office goes back years. It used to be a free add-on to SharePoint and allowed up to 64 simultaneous users per document.

I believe the current Office 365 came from that codebase as it has similar features.

Can you not effectively use it as such, however?