When we last stayed at the Contemporary in 2019, that patio was a great place to view the fireworks and then since we were already at our hotel, you didn't have to fight the crowds leaving the park when it was over. We could see all of the fireworks and whatever the light show on the castle we couldn't see, but enjoyed everything else. Anyone staying at a monorail resort could view the fireworks from there. There is no restriction on which other monorail resort can visit the others (Polynesian monorail stop currently closed for construction). There was plenty of seating and not that many people there. As I recall, part of the patio was closed off one night for some sort of private party taking place, but the other part was still open to the public.
The parking situation relates to people trying to game the MK parking fees (park for free at Contemporary then walk to MK) and Disney is wise to that. They also don't want the parking lot to fill up with MK guests such that those actually staying there have no place to park.