>>718935743
A franchise is more than just its gameplay. Pacland and the other spin-off Pacman games share very little in common with the traditional Pacman gameplay but they're still easily identifiably Pacman. You don't need to stick to a specific type of gameplay for it to be a game of that franchise.
Another good example are the Touhou games. The first game was more of a Breakout game than a traditional SHMUP, but you also have fighting games, but they're all still inarguably Touhou games.