IRC works and has worked for decades. Its minimal, text-only, no bs, no distractions nature is its greatest asset. Client support, programmability, and ease of integration too.
The folks that like Matrix are already using it. The folks that have stuck with IRC for decades will not abandon it for a protocol they deem to be inferior.
You don't even have to go "all in" on all the fancy new Matrix stuff; just write a wrapper to comply with being a "homeserver", and continue using the IRC API with no changes. If not, that's also fine, I'm not that invested in this personally.
When the matrix gateways go up and down you'll have 1000 random users thunderously join and part the channel at once.
Matrix comment edits flood the channels.
Matrix is unhelpful with abuse reports, in my experience.
I generally ban matrix from IRC channels for these and other such nuisances.
In terms of abuse reports; Element hires a fulltime team of folks to man abuse@matrix.org on behalf of the Matrix.org Foundation and chase down the tickets as they come in. Please ping abuse@matrix.org if we've dropped stuff.
Seriously, I think message length limits are the main thing that's holding back the IRC protocol. If you can send e.g. 65536 byte messages, anybody will be immediately able to create scripts for sending images or code snippets.
Please encourage your favorite client's developers to implement it if possible.