You can still put a web client with persistent chat history in front of IRC. TheLounge is one example [1] [2] and Convos is another. [3] [4]
[1] - https://thelounge.chat/
[2] - https://github.com/thelounge/thelounge
[3] - https://convos.by/
[1] - https://thelounge.chat/
[2] - https://github.com/thelounge/thelounge
[3] - https://convos.by/
FWIW, there are also shiny front-ends to NNTP. That would actually be a great way to have a threaded messaging system and attachments.