A small fission reactor is also incredibly dangerous and will always require exotic material.
A fusion reactor does not pose environmental risk and could eventually run on highly available basic elements for everything after the initial "startup" once the technology progresses.
What exotic materials? Molten salts and steel is most of it. These reactors have essentially 0% chance to have airborn escape of radiation.
An fusion reactors don't actually run on basic elements. The require a fuel that is specially breed. And when they operate they have radioactive materials that can go airborn.
https://www.moltexflex.com/flex-reactor/
A small fission reactor can do almost everything a fusion reactor can. Fusion fuel is higher density, but fission density is already not an issue.
Fusion still needs to heat water, that's where much of the cost comes from.