Those... are not mutually exclusive as killer upgrade. No longer having to use a nonsense CJS syntax is absolutely also a huge deal.
Web parity was "always" going to happen, but the refusal to add ESM support, and then when they finally did, the refusal to have a transition plan for making ESM the default, and CJS the fallback, has been absolutely grating for the last many years.
Especially since it seems perfectly possible to support both simultaneously. Bun does it. If there's an edge case, I still haven't hit it.