I haven't had a problem with apt since I was using Debian Unstable (sid) back in 2005... and even then, I think I installed stuff from other repos that conflicted with the base system.

Portage is cute but it's tied to Gentoo and few people want to compile their own packages.

Apt was one of the earliest package managers for Linux, for a popular distribution. That was enough to give it a head start regarding packages available. And that's all you need, unless the other solutions are obviously superior from the user perspective, which they're not.