As someone who is currently on the planning committee for the second year of an
off-season event, I can say that planning for a small (less than 24 team) event can be very challenging.
Last year we didn't actually know how many teams were going to show up until the day before the event. The alliance structure of a FIRST competition is highly dependent on the number of teams there, especially when you have less than 24, so it doesn't surprise me that changes would be made last minute. Heck we were still finalizing our alliance rules at lunch time on competition day. It wasn't because we wanted to, it was because we had no choice.
I can't speak for the rule changes at your event, but at ours we generally try to make the rules more relaxed without adding more complications to the game. Our event's rule changes were released about 3-4 weeks prior to the event after looking at what other events had done and coming up with what we thought was a good balance. Would we have liked to release them sooner? Sure, but when you have a planning committee that meets only once a week (or less) and consists of volunteers that usually have day jobs to deal with too, we get the information out when we can.
Finally, I don't know what caused the date of your event to change, but try to keep in mind that almost all off-season competitions are completely at the mercy of the venue. If our school were to say to us "sorry, something came up and we need the gym that day", we would try our best to work around the issue but ultimately we too might have to change the date at the last minute.
Now, obviously, I was not at this competition, I do not know the people in charge there, nor did I share your experience. But I hope you consider that there's a lot of things that go on behind the scenes that aren't always within the control of the event organizers who, generally, are just trying to do their best with the resources they have.