I will stand by this to the death. The mechanics are forgivable, but the story?
You build on what you have and tie everything together into a connective whole that would work with itself, not against itself. You leave mystery in your wake, not rage and fatigue.
Players should never look at the realms beyond their own and go “Urgh, that place.” with the same level of disgust we reserve for having to use a McDonalds Bathroom in the middle of the bad part of town.
Rather than a whole brand new Titan++ threat, it is more Titans we’ve never heard of. The lore is revealed that they were explicitly removed from history to prevent rebellion and alienation towards the Titanic Pantheon, and even some Titans do not know of these ancient beings still existing.
We don’t just pop over into the Realm of Death, we are Mortal, it doesn’t matter how powerful we are, we cannot survive that trip, or at the very least is is a permanently one-way trip. Instead its a Titanic facility composed of interlinked prison-Demiplanes just on the edge of the Material Plane and Death, and the true Shadowlands remains a mystery to us all.
Jumping the shark for the sake of it never works well, and cheapens everything the players have done to get this far, and doing that over and over and over and over just makes players feel like “Why even bother if everything I’ve done can be wiped away by this new even greater threat pulled directly from the 
's 
writing all of this?”
Is tackled off his soap-box and taken outside to be violently rolled on the grass