Mozilla Company refuse to use IRC as the main platform for live communication between project participants. The IRC.mozilla.org server is scheduled to be taken down in the next few months, following a migration to one of today's web-based communications platforms. The decision on the choice of a new platform has not yet been made, it is known that Mozilla will not develop its own system, but will use the popular ready-made solution for text chats. The final choice of a new platform will be made after discussion with the community. Connecting to communication channels will require authentication and consent communities.
The reasons for abandoning IRC are the moral and technical obsolescence of the protocol, which in modern realities is not as convenient as we would like, is often blocked on firewalls and is a serious barrier to connecting newcomers to discussions. In addition, the IRC does not provide proper tools to protect against spam, abuse, bullying, and harassment by members.
Source: opennet.ru