Mozilla is by the way also of the opinion that a monoculture would be horrible for the web. Arguments that I've heard from Mozilla employees:
- Without competitors, innovation is dead. If there was only one web-engine, why bother improving it further? Given that it's open-source, it could theoretically be forked, but in that moment you again have two different web engines or more. Also, Mozilla would have to fork Blink from day one, because many things in it, they do not consider acceptable.
- A monoculture means one security problem makes everyone vulnerable.
- Multiple implementations challenge standards. You still would want a definition of a standard, or an API if you will, to point web developers to. But those are only going to point problems out after you've already implemented it, and likely also after other websites are already using the feature productively. They also can't point out stupid specifications that aren't going to allow you to update your browser engine in the future. So, you'd be much more likely to have to break compatibility, which doesn't play well with the web.
- Without competitors, innovation is dead. If there was only one web-engine, why bother improving it further? Given that it's open-source, it could theoretically be forked, but in that moment you again have two different web engines or more. Also, Mozilla would have to fork Blink from day one, because many things in it, they do not consider acceptable.
- A monoculture means one security problem makes everyone vulnerable.
- Multiple implementations challenge standards. You still would want a definition of a standard, or an API if you will, to point web developers to. But those are only going to point problems out after you've already implemented it, and likely also after other websites are already using the feature productively. They also can't point out stupid specifications that aren't going to allow you to update your browser engine in the future. So, you'd be much more likely to have to break compatibility, which doesn't play well with the web.