Do you want to run an action automatically for every single event when it starts, or would you like an action that you can run that will retrieve the current (or next?) event details and create the draft from that?
When you say “opened with the date and meeting title”, do you mean on separate line or a single line? Is there any formatting you want to apply (e.g. level 1 Markdown heading, standard ISO date format for the date and a colon followed by a space separating the date from the event name).
Do you ever have overlapping calendar events, in particular calendar events? If you do, you might want to consider having a user prompt to select the event for which to create the draft.
That could be useful for scheduling a check on your calendar and triggering an action if you did want to automatically do things. But, do keep in mind if you do want to automate that far then you could end up automatically switching away from something you are doing.
Also if you wanted to have a global hotkey you could trigger from any app to run a Drafts action to create your meeting draft, Keyboard Maestro would be a good option (you can trigger an action via a URL call).