Balance have only been broken when Luffy became Yonko and awaken the God fruit
world govt will be aight if anyone other than luffy ascended
hence they want Marco to be yonko instead of Teach lol
Teach and Marco doesn't relate to this
Ofc you would rather a D that can eat multiple fruits and is hella ambitious doesn't take power over some dude just chilling.
Balance had plenty of chances to be broken
They each have one piece of the puzzle to Laugh tale
They could always ally with each other to try to take the one piece like they actually did.
They could ally with other people like they were about to with Elbaf.
They can make stronger weapons like the Germa tech, smile, gas etc that were being used.
They could discover the ancient weapons in Wano etc...
There is a lot of reasons to get rid of them specially when it doesn't take that much and they are actively building up their strength to oppose you.
But even if you ignore Kaido and Bigmeme what is the reason Teach is still alive?
Why not just summon all the Gorosei and HK during one of his parties and just neg his ass when you know he's a problem?