The issue is how many of the new ips they created in the more recent years were actually good? Elemental was good, and found legs. The majority of the original stories were at best just meh. It's hard to judge peoples reception to original ip, when all we've really seen is mediocre to bad for the most part.
Of course they do. If there's a story to tell, tell it. Moana in my opinion was done a disservice with it's sequel. It wasn't near up to the quality it should have been. That's the problem with sequels in my opinion. Toy story 4 was terrible and not needed at all. Cars 2 & 3? That was just to sell toys. You could tell they had no real plan for frozen 2. When they make sequels because they have a good story to tell, great! I'm all in. But as you say, Disney can go sequel overboard like you said with toy story. I'm all for a frozen 3 & 4 if they actually have a story to tell. If it feels like a cheap cash grab, people will complain.