I normally find turn-based combat really boring but I find Shin Megami Tensei games so engrossing in part due to the combat. You need to pay attention to mechanics and properly prepare for each boss fight if you want to overcome them. It's not about just gathering enough exp. Do you know any games similar to SMT when it comes to gameplay?
Does it have to be a JRPG? If you want tactics in your turn-based games I recommend looking into cRPGs as the genre originally started as adaptions of tabletop games and has way deeper tactics compared to most JRPGs. Stuff like the Baldur's Gate games, Dragon Age, Wasteland, Divinity: Original Sin 1+2 or Arcanum: Of Steamworks and Magick Obscura are all turn-based or real-time with pause which work similar enough to count. As a plus point most of them allow you to be rather creative in the way you play from stuff like talking an opponent into killing themselves to turning opponents into chicken and letting them bleed out with another skill.