When one person organises everything for a group there are usually problems. In my family we have someone who likes to organise things. She likes to decide when and where things are happening (so they are convenient for her), the type of event, eg a party/dinner/whatever and so on, and to be toasted for her generous input.
All of that is fine, and it's fair to say that she does put the work in, but it can be galling to be told 'this is happening on X date at X time' rather than 'what are we going to do about a big birthday or other celebration?' and invited to join in with the decisions, rather than be treated as just another guest at a 'do' for a shared relative, who may or may not be able to attend at the time and place she has chosen. There is no room for input from others, as we are presented with a fait accompli, and just have to go with it.
Also, there is a 100% chance that as the day gets nearer she will delegate big tasks, with no consideration for how convenient or otherwise they might be - 'I thought you might like to organise the food', 'Can you pick up 3 elderly relatives (who live miles apart from one another in different directions) and get them to the venue?' or 'I suggested that X stay at your house the night before as that would be easier.' It's maddening. Often the 'requests' are prefaced with 'As I have done all the arranging. . .' when she took it upon herself in the first place.
It would be much easier all round (and possibly for your group too) if there were a meeting, either in person or over something like Zoom, where everyone gets a say in what happens from the start, and tasks are divided equally (or according to who has more time) and above board. That way there could be real input, nobody feels resentful and overlooked, and everyone can opt into or out of suggestions before they become demands. Also, when everyone has an input and there is a broader range of suggestions the odds are greater that the end result will please everyone.