>>39878753Making a mainline game on the new console took them longer than they initially thought, and the series needed something to fill in the blanks to avoid having too much of a blank window.
It's the reason why they allowed the franchise to be used for something as low quality as Pokemon Dash (which was something unprecedented for the series at the time, believe it or not), and why they allowed so many contractors to work on spin offs while they main office focused on getting DP out of the door as soon as they could.
Nowadays that spirit of innovation is completely dead.
New projects are only made as a corporate controlled source of revenue, and they could pump out a mainline every year if they wanted.