The game director determines what the gameplay will be.
Final Fantasy 7 Remake trilogy game director Naoki Hamaguchi commented in a new interview on the success of Clair Obscur: Expedition 33 and its possible impact on Square Enix's strategy regarding the Final Fantasy series. Hamaguchi noted that despite the game's warm reception and increased interest in the JRPG genre, the company does not plan to predetermine whether the next game in the series will be turn-based or more action-oriented.
For numbered Final Fantasy games, the design is determined by the game director's decision. Whether the new game will be an action or turn-based RPG has not yet been decided. It's important to me that players enjoy themselves. That's the key goal.