To me, the Titans are essentially DC's Fantastic Four (or were). The NTT, especially, were a group of seven people who came together for an initial reason that eventually gave way to them staying together because of the bond they shared.
Wally left, to be replaced by Jericho. Much like Thing and She-Hulk.
But Titans eventually came to be the book you read for those characters.
One thing it had going for it, that the FF didn't, was that there was no clause that you had to be a real family member to join.
Membership in Titans was open to those that the team would accept into their artificial family.