+m quiets all users in the channel and only allows you to speak if you receive the channel-user mode +v (voice) or have +o (operator status). Some ircds also have a +h etc.
You can setup bots like “RaiseYourHand” for people who want to ask questions and need temporary voice (+v).
Try that on slack, telegram, signal, etc. Its impossible.
IRC was ACTUALLY built for collaboration and communication. Slack was built to make money.
The difference in goals causes a different outcome.