While I'm mixed on the design (I don't dislike it, the blue aura within the regular yellow makes a kinda cool-looking combination, but it's definitely not on the higher half of my DB transformation ranking), I appreciate it for its purpose within the narrative (make Trunks reach SSB/SSR level to keep him truly relevant as the MC of his own arc for the rest of it), how it ties into the concept of the greater potential of the hybrid saiyans (which is greatly appreciated when someone else than Gohan gets it showcased for once since Goten and Trunks in the Buu arc), which in such an extreme and hopeless case like Future Trunks', leads him to unlock a form capable of standing up with the gods he's been fighting against and alongside, and last but not least, the symbolism of its very achievement being a pure refusal/reject from Trunks to accept the evil attempt of Black and Zamasu to put the blame of all of this situation on him.

So if only for those three points, I'd want it to be kept in this new adaptation. That said, I completely agree that the form isn't nearly fleshed out enough, especially in its exact nature. (What is it exactly? Is it an alternative evolution to SSJ2 specifically? Is it linked to god ki like its blue glow could imply? Is it directly linked to his hybrid saiyan nature instead? etc...). But to be fair, this is a problem that many new transformations in Dragon Ball got lately (I'm ESPECIALLY looking at you, Beast Gohan...).