By now requiring users to go and contact chanops to ask them to explicitly plumb IRC channels to Matrix, it's just going to waste time for chanops, precipitate weird cross-plumbing failures, or fail outright (given plumbing channels with more than 100 users has to be done manually to prevent abuse).
It's very unfortunate that it's come to this, and I can only hope that the whole "opt in with a chanmode" thing happens, if portalling is off the table.
In fact, wouldn't it have been better to just ban the bridge by default, and let chanops unban it if they want people to be able to access via Matrix, rather than encourage people into the weird world of plumbing?
EDIT: clarifying that i'm not neutral on this, given i'm project lead for Matrix, and also responsible for running the Libera bridge at Element.