(From kerraig, I knew he'd wanna respond to this)
Time hasn't been kind to Dawn of the Dead simply because of the limitations of its budget and the scope of its ambition, but you simply have to put it into context. Very few films by this point had grappled with such huge themes in horror: What do we do when a global supernatural phenomenon affects absolutely everything. Something that isn't aliens or terrorists, but is something existential like death no longer being death. Being forsaken by God, existing outside of ourselves and our own consciousness.
This is riffed upon in so many clever ways. What does a talk show look like when ratings dont matter? What do the religious poor do with their dead when the government demand the bodies are handed over, where do you escape to when the thing you are trying to outrun is death itself? do trinkets still have any meaning in a post consumerist world? what is the point of getting married?
These themes are handled quite clumsily because the film was made by amateurs at night on a shoestring budget, but nobody else was dreaming that large at an indie level at the time. Kubrick and Bergman and Kurosawa were the ones tackling the big themes and they were doing it with all the backing of their studio or their government. Dawn really searches for the big questions and really tries to make you care about humans and humanity. It's very creaky now and almost impossible to go into cold. But for the time it is absolutely beyond seminal.