Sounds like a skip for me.

One. One single Engage character. I know Engage didn’t sell as well as Three Houses (I vastly prefer Three Houses myself), but IS really doesn’t need to try to bury it like it doesn’t exist. If they’re concerned about reception among fans, from what I’ve seen it’s still not the worst received in the series (that “honor” goes to Fates, IIRC), the gameplay holds up even if the story doesn’t very well. Three Houses is the best selling and possibly the most critical and fan favorite game in the franchise. It would be a tough act for any of the other games to follow. Not selling as well or getting as warm a reception as your franchise’s #1 game is not automatically a failure.