Its hard to compare outside of the strategy genre, but even then Diofield is real-time w/ pause and triangle was straight up old school turn based.
I don't know what to say about Diofield yet tbh.... The art carries it hard. Some beautiful stuff fr. Outside of that, there are a lot of little things that make the game seem like an open, unashamed scaled-up mobile game. There's a lot of leveling mechanics that seem to stretch the game needlessly, they lean on FF jargon for attacks and summons, the UI doesn't seem it belongs in this gen, etc - its really small stuff.
Diofield isn't even a legit 'bad' title.
It just feels like something pushed out the door and more disappointing than anything because everyone playing can see the potential. Cut corners stand out hard in strategy titles so a lot of jank is hard to ignore.
Also, anyone who can't deal with story marinating is just not gonna like Triangle Strat at all. That's biggest divide on people appreciating that game by far. Diofield's intro is a lot more attractive, yeah, but its still goofy as fukk and you'll care about no one outside of their stat sheet really.