After years of maintaining packages, I think I decided that much of the complexity is unfortunately warranted. You want stuff to work in all sorts of situations, with all sorts of different other things installed at the same time. You want upgrades to work. You want tests to work and to run, but probably you want to skip them when cross-building. You want the package to be co-installable across architectures. You want the package to be cross-buildable and to be usable to cross-build other packages. And you want your builds to be reproducible. And lots and lots of other things, all the while having to deal with upstreams that often don't care about many of these things.
I haven't seen any other packaging system that is both nicer and maintains Debian's high standards. Maybe something exists. I think Debian's biggest problem in this area is the documentation. The official docs should be more accessible, but that's a big job that nobody has stepped up to do. Yet.