SB MCH was at a dead end... Because of how Wildfire used to work.
Every new cooldown they could add would be incorporated into Wildfire combo. Making the combo bigger and complex until you can't weave anything in there.
And at this point, it would be choosing what to cram into wildfire.

For a quick reminder, SB Wildfire was meant to eat all damage, not just GCD to increase its potency.
If I play MCH it's for its visuals and appeals, I don't care about any other DPS or gameplay.

One point about complexity:
Flamethrower and tick fishing is one of the most complex (and annoying) aspect of MCH.
It's not a fun tool to use in AoE or tick fishing case.

Casuals don't use it the optimal way, they don't actually care about the optimal way, yet they are adamant on keeping it.
If a button too complex was to be added, same scenario would occur.

Like how many of you probably experienced the "Healers shouldn't DPS" and any other jobs played wrong.
They don't care about optimizing complex rotations, but they fear its existence.