I agree with @ddmiller: this doesn’t look like a revenue generating move to me. I can’t imagine Apple will increase revenue by any noticeable amount by turning off My Photo Stream. This looks entirely like a, ‘why are we spending engineering resources and increased complexity for a feature from a different era that ~nobody uses?’ decision.
I’m sorry you had that problem, but maybe it was because you hadn’t disabled iTunes syncing first? All I can say is that I’ve used iCloud calendar sync for many years, with several calendars, and sharing different calendars with different people, and it has been 100% solid. Maybe backup your calendar and try again (so you can easily clear it out and re-import the backup if you have trouble again), but first turn off any other sync mechanism?