But kids don't make your schedule, set your reservations, or feel the burden of paying for the trip. Disney has built this model that conditions you not to eat when you are hungry.. but to decide months in advance at 1:30 you will eat at this spot.. You don't decide "lets ride space mountain!" someone already decided at 4:20, you are supposed to ride space mountain. That time inbetween? You can adlib.. but you know you have a commitment.. so if you were to head to TSI for instance, the exploration is going to be cut off. Now instead of playing a game, a parent rushes their kid through each portion to 'finish' before their time runs out.
The dad doesn't want to spend $500 for the day to watch their kid play with a rock... just like people who end up watching their kid enjoy the hotel pool instead of wanting to go do all the other stuff they've already paid for.
And I don't care what you think kids need or not - we're talking about what Disney has setup. You can try to ignore most of Disney's model, but you're going to be getting a vastly inferior experience while paying the same amount. People aren't going to do that in the long run.
Disney's model shapes and influences consumer behavior. From the marketing, to the structure, to the constraints.
But what you're describing means the parks need
more experiences like TSI, rather than fewer. With so many parts of a theme park day being pre-scheduled now (attractions, entertainment, dining, etc.), downtime between appointments in inevitable, so they need ways to fill those odd amounts of time.
However given the configuration of the parks, it's exceedingly difficult to find a rewarding way to kill 20-30 minutes while waiting for your next appointment time. Even minor attractions and character meet & greets routinely post waits in excess of 30-45 minutes across WDW, and that doesn't account for the time to actually experience the attraction itself. If you're trying to fill in the gaps, there's really not much to choose from.
Playgrounds and free-roaming areas like TSI, Innoventions, and countless post-show areas that have been whittled away over the years are the perfect solution that problem, as they're able to absorb guests with typically no wait and provide a worthwhile experience, regardless of whether a guest spends 10 minutes there or an hour. Yes, the rafts made the logistics of TSI more difficult than a standard playground, but in a typical afternoon guests could still take the raft over, explore the island for a while, and take the raft back faster than they could wait in line and experience nearly anything in the park. Similarly, the animal trails and Journey of Water are saddled with their linear layouts making it difficult for guests to tailor the duration to their needs, but they're still quicker to experience than other nearby attractions.
Disney themselves acknowledged this would be a problem during the development of MyMagic+, and added several lounge spaces (before "lounge" was Disneyspeak for "bar") to the parks as part of its rollout, with places to sit and recharge phones. Most of them were far from busy areas, poorly advertised, and offered nothing of interest, so they were seldom busy. Instead guests piled up in the crowded walkways and near their next appointment destination, making congestion worse in the parks. Few of the lounges remain in the parks today (notably, the woodsy seating area between the Tangled Toilets and the main walkway), since shockingly not many people wanted to pay theme park admission to sit and watch their phone charge.
Not everything on a park's menu needs to be a main course or a dessert: there's room for palate cleansers, amuse bouches, and lagniappes to round out the overall experience. They may not be the reason that someone comes in the first place, but they're the small things that make the whole day feel special and encourage you to return in the future.
Instead of having minimal-wait varying-duration diversions to fill the gaps, or even dull lounges to kill time, the parks are increasingly left with nothing. If the wait is short enough, you could always grab a snack to eat while standing over a trash can; you probably won't enjoy your day as much and won't be as likely to want to return in the future as if you had spent that time enjoying a minor attraction, but at least Disney gets a couple extra bucks from you today!