My least favorite is Digimon world 4. It felt like a non-digimon game that they crammed digimon in.
I wish they had digivolving as more of a core mechanic; you only digivolved once in that game and when you did you needed to basically restart the game from level 1. I also wish the game/combat wasn’t so grindy. Sitting in one spot mashing the attack button was the best strategy most of the time and… just wasn’t fun.
Honestly, I’d just port the Digivolution mechanic from Survive (and thus, the anime) to the Story Games. It’s kind of ridiculous how Digivolution works in those games, having to do it as a side activity feels too inspired from Shin Megami Tensei/Persona. I’d rather undertake quests to unlock specific, branching evolutions for my Digimon partner(s) and then evolve them in battle.