Which was actually true of TOS as well because there really wasn't any tension between the characters there as well. Sure, Spock and McCoy occasionally got into disagreements and traded barbs with one another, but it wasn't like they hated one another.
The only real difference with the TNG characters was that their disagreements were more civil and didn't resort to name-calling.
But with both TOS and TNG, the main conflicts involved characters who weren't members of the crew (the sometimes referred to "conflict from outside").
This is one of the reasons why DS9 is so good for me. There's some real tension, there, although of course it fades between the main characters as the show goes along.