Genesis 11:6 seems to be really badly (or at least ambigusously) translated in many versions. They say something like “…nothing they plan will be beyond them…”. That’s not, and can’t be, what the verses means.
Such a translation makes God sounds like the Egyptian pharoah of Ex 1:10-12 – scared that mankind might equal, threated Gods authority and somehow steal God’s position as sovereign creator. That’s what many translations seem to make the verse say. God is a scardy cat.
However, with an understanding (and better translation) of the verb used to describe mankind’s actions, all becomes clear. The verb used is זמם.
The verb is used in e.g. Deut 19:19; Ps 31:14, 37:12; Prov 30:32 to talk about the planning of evil (See also Holladay). The relevance of this for Genesis 11 is that God is not seeking to stop mankind from ganging up on God. Rather God is seeking to stop mankind from too much evil. God’s judgement on them for the Tower was also an act of grace. God is not fearful of his position; rather he is fearful that man is going to increase and be able to accomplish more and more wickedness.