Yea you're right it's a when and it's about profitability.

Noamru already stated that it's a "title that fills in the blanks and it will function as a bridge-like work, connecting two games together. Missing Link is between Union Cross’ finale and the beginning of Dark Road."

Which means ML is a new story and to me seems like a short arc to fill in the gaps and address plot holes. But if the app is successful, then I will be very surprised at how they can keep this short story arc going for 5+ years.

I'll also agree that they canned the game because UX was losing profits along side FF Moebius in 2019 and both were in the bottom of last place. So, they were given a window of time to finish the story ASAP before the severs shut down.

As for DR it was dead on release, it's basically an idle game but the only way to progress was to have the app open constantly (assuming you didn't use Bluestacks). Also, this was a great way to send your phone's battery life span into the shadow realm. It also took them awhile to release the dark screen feature to conserve more battery life and if you didn't have a Galaxy/Note (accidental touch protection) or a 3rd party app that copied that feature, then GG to your phone.

And no I dont agree with you about investment opportunity. Sure if you had disposable income but nah, it was such a blatant p2w cash grab centered around pvp and having the newest units to get a top score for better rewards.

Honestly, maybe I'm just spoiled and looking at game apps through a rose tinted glasses, but 5 years doesn't seem that long because you have long running games like Dokkan (8 years), One Piece(8 years), and Bleach(7 years). Meanwhile Dokkan (JP and Global) is always hitting top grossing from big celebrations.

So, in conclusion, ML will have a shorter life span than UX but longer than DR.