When an upgrade isn't an improvement
A major-version upgrade has an opportunity cost. Postponing can be technically responsible when support is intact and new capability does not advance product or architecture goals.
Major-version upgrades are often presented as defaults, but they are product decisions as much as technical decisions.
Every upgrade competes with architecture work, security hardening, delivery commitments and modernization efforts already in progress.
If the current platform is supported, and the new version does not materially improve product capability or architectural direction, postponing can be the responsible engineering choice.
architecture
platform strategy
maintenance