The problem is that DHS simply doesn't have enough other attractions, especially family friendly ones.
It'll also be interesting to see how well that works. I think the Door Coaster, as a suspended coaster, will scare off some kids that happily ride Slinky, and of course there's already RNRC for people that want something more thrilling.
People are going to want to ride both so I don’t see how that helps.
This is not the Door Coaster thread so I'm not going to really push it in here any more than this post.
Slinky Dog Dash commands a 38-inch height requirement. This is a height most 4 year olds can achieve. A number of guests to the parks are under this height limit, but man, I can't imagine taking a family down to Orlando unless at least one/majority of the kids were at least 4 years old and had credibly developed the capacity to form memories. It's not as family friendly as not having a height requirement, but it's pretty close!
Slinky Dog Dash is... fine. For being "fine" it commands a frankly egregious wait time. What does that mean? There is a general demand for attractions that meet or exceed that quality and flavor of experience that is being severely underserved.
Disney does want people to have happy and successful feeling visits, because it gets them to spend more money. The theory around this is complex, but be honest with yourself: have you ever completed every attraction in DHS in a normal day in it's post 2019 configuration? Probably not! Have you ever had the same visit twice, where you do the exact same attractions the same amount of times? Probably not! Do you think every guest has the same goals in a given park visit as you? I would hope not!
There are groups who want to go specifically to enjoy the Toy Story rides. There are groups who want to go to see the stuff added since their last visit. There are groups who want to cover all of the roller coasters. There are groups who want to see all of the shows. There are groups who want to buy as much crap in Galaxy's Edge as they can cram in the plane trip back. I want to ride Tower of Terror at least 3 times.
Meanwhile, while the attraction will generate 15,000 new experiences a day, over a tail beyond probably 9 months at most, it will not drive more than 15,000 additional unique visits a day.
More guests will have more satisfactory trips with this addition. They'll either have this specific new experience to enjoy, or will benefit indirectly from the crowds that go to it and leave other attractions available. If a family finds the idea of the Door Coaster too intense, but not Slinky Dog, they will likely enjoy a significantly shorter wait time than if the Door Coaster didn't exist. If a family feels like they need to ride at least one of the two roller coasters, they'll benefit for the same reason. If they don't want to or can't stand in line for either, they'll enjoy lower demand from people who now feel better served by having the new ride.