I probably have a much lengthier ramble in me about this at some point but
I firmly believe that the core building block of any good tactics game is The Recognized Opportunity
- The enemies standing next to each other that you can catch in a plus-shaped AOE
- The high ground you can use to snipe without return fire
- The geo panel you can set off with just the right throw combo
- The enemy just waiting to be pushed into the ocean
- The extra distance that gives you just enough time to throw up that vital buff
- The cover that has just that perfect line of sight on the hallway
- The wall that makes the perfect entry point if you blow it up
I firmly believe that it is the job of the tactics game designer to create, not ""challenging"" systems but ones that Suggest Opportunities to the player. A good skill or job system immediately makes you think about what you could do with it, in isolation and in synergy. A good level design lets the player look for things they can take advantage of and maneuver around.
A tactics game lacking these elements often devolves into a simple slugfest where ganging up Just So is the only leverage you have. I have played more than my fair share of games like this. They are excruciatingly boring.
I would really recommend any newbie tactics games designers think hard about what opportunities your game is flagging. Think of the ways the games you like telegraph them - Differently-shaped attack radii, terrain features, conditional abilities, etc - what are they offering to the player? How often are they offering these different opportunity types and how do they vary? What about it is it interesting? What makes it feel worth it? What feels fun about it? Please don't just clone FFT's mechanics without considering why. I promise it is a recipe for tedium. FFT works very hard in its level design, enemy design, move and job design, to offer the player a lot of interesting opportunities, from the small and frequent AoE to the complex long-term metagame job combination.
To go on a tangent for a minute, the details matter on these things, too - Recently-ish I played a demo that featured positioning-based skills and chokepoints for player advantage. The game also gave everyone - enemies and players alike - colossal move radii, resulting in every single fight having a single initiation round and then everyone was immediately in each other's face. The result was that positioning became immediately irrelevant, because there was no opportunity cost for anything - precise moves had 100% uptime because repositioning every turn to make them effective was trivial, rendering weaker, less position-relevant moves pointless. If you had a strong ranged attack and a weak melee, it didn't particularly matter, because you could simply gain the necessary range every round. Why even use that other move? At the same time, defensive, wall, and trap-type skills became nearly irrelevant because circumventing them was trivial. There's no opportunity to get your weaker characters away from enemies when everyone can move the majority of the map in a single turn. With this single, simple-seeming choice of move radii, the developer seriously harmed their players' ability to spot, create, or take advantage of any of the opportunities the skillset offered.
Considering this kind of stuff is an absolute minimum to make a decent tactics game at this point. What are you offering, can players see it, and can players actually take advantage of it?