[SubiculumCode]

Backwards compatibility was not an option for Mozilla to move their architecture forward for a modern multi-core computer. A rational person would understand this and move on, or find a way to support a fork of FF 56. I have been a user of extensions since the earliest days of Mozilla Firefox (and earlier) and I love the new browser.

[wtallis]

The migration to a multiprocess architecture was handled relatively painlessly early this year. It had nothing to do with the migration to WebExtensions. Many extensions were incompatible with the multiprocess Firefox architecture, but when the user had one of those extensions enabled Firefox simply fell back to using a single process. Many popular and well-maintained extensions were modified to be multiprocess compatible without widespread user-visible breakage or loss of functionality.