I think the frustration comes from airlines not being able to accurately predict what the impact of a delay will be for the schedule for the remainder of the day, following day. They always hope they'll be able to recover some of the schedule with fast turnarounds.

On a recent trip (when I encountered issues on every leg — cancellations, delays, missed connections, you name it), it is clear that airlines are incentivised to not communicate delays until it is clear the delay can't be recovered. In one case, at the airline's hub, the airport displays were showing a 2 hour delay and their app showed on-time departure (to the point I had to go and ask which source to trust). Having been a frequent flyer in the past I was able to determine that the delay was likely (but airlines can swap in equipment at hubs and mitigate the delay).

Once you do have a delay the ripples are complex to handle. You have some passengers that were meant to connect to other flights. You have some that won't travel at all die to the cancellation. You then have 100+ people who you somehow have to accommodate in the coming days when flight loads are hopefully already 90+%.

To be fair to my airline, their app was actually great at offering me a rebooking option the following day when my flight was cancelled. Unfortunately, the option I selected resulted in a non-direct flight with a transfer time that was impossible in reality (shouldn't have been offered in my opinion). I was literally rebooked 5mins after they declared the flight cancelled, skipped the queues back in the departure area (I don't think the local service agents even knew about the app) and drove home to my family for an extra night.