We have one bad guy (jailer) that is trying to rewrite the order of the universe ( okey this is maybe liitle exageratted but u know what i mean) and where are titans when we need em ? What are they doin ? Fighting voidlords ? Or just watching and lets see how things goes on ?
Well i dont expect some dragon ball z planet crushing style show with throwing atomic bombs on jailer but atleast some small amount of care.
Titans are kept away from the story because of how powerful they are.
They are currently busy sealing Sargeras and Illidan is his jailer, so they cannot go anywhere or Sargeras will be free, and if Sargeras escaped or was freed from his prison then the burning legion will return and the whole universe will be in danger.
The only answer I can give to you is the one that I got from an interview about the BfA story.
When we sat down to talk with Steve Danuser, Warcraft’s senior narrative designer, and lead artist Ely Cannon about the Horde’s identity in Battle for Azeroth, we made sure to bring up World of Warcraft’s missing spaceship as well. Danuser:
We wanted to focus on key characters like Sylvanas, Anduin, Saurfang, Greymane, the embodiment of their sides, and really show that gritty, in-your-face, toe-to-toe, siege-towers-against-tower-walls [action]. That was the story we wanted to tell.
So, there you have the approach of the current narrative lead. Everything is on indefinite hiatus till the devs feel like using it for a moment when convenient for the story.
[since titans are not what they want to talk about now, there are no titans]
They would not be any use against that “Final form” jailer we have seen in leaked screenshots. He is stated by authors to be titan++ power level currently as he is.Right now in his imperfect form he can be beaten by sargeras 1v1 as Sargeras soloed entire pantheon which means he is on the same level or even higher as jailer now. But with his perfect/completed form his power lvl is so high that titans are useless same as eternal ones are. I think only first ones can defeat him at that point. Or if Void lord manifested in material reality and erased his existence by mere presence but that is hard for them to do if not impossible due to their abract transcendental existense beyound dimensions/time/space. Maybe it is time for us to loose in this expansion, as i do not see way we defeat him, if azeroth wakes up it can change as she might be multiversal level being.