Genesis 11 starts out with the story of the tower of Babel. It shows what man can do when united. The problem is that they were doing it for themselves and getting prideful about it. The other issue was that they were limiting themselves to one location. Continuing on that path wouldn't lead anywhere good. They wouldn't have acknowledged the fact they needed a Savior or populated the earth.
God isn't and wasn't against unity. Look in later scriptures and you will see repeatedly where it talks about how He wants us to be united. United in love for one another, working on spreading His love and good news, so none should perish. He saw the big picture and they were caught up in the moment.
The second half of the chapter goes through the descendants. This shows after the flood people didn't live as long and as the genealogy continues it decreases even more.