Multi-device with history is not built-in to the spec which makes it a non-starter for big rollout. IRC has had many years to adapt but it didn't so here we are.
As someone who was essentially constantly on IRC back in the 90s to early 2000s, IRC is just significantly less usable "out of the box" than Discord or Matrix; either is significantly easier to teach someone to use, especially multiple-device.
The ship has sailed and I don't think IRC3 will ever get traction even if it ends up actually being good.