Measure the real constraint
Separate visual age from business impact. Look for delays, unavailable skills, security exposure, fragile integrations and changes the business can no longer make safely.
A system that is quiet, contained and dependable may deserve less attention than a newer platform creating daily friction.
Choose an intervention, not a slogan
Modernisation can mean documenting, isolating, integrating, replacing one component or rebuilding the whole product. Those choices carry very different cost and risk.
Start with the boundary that reduces the most material constraint without creating unnecessary migration work.
Plan the transition
Replacement succeeds when data, users, operating rules and fallback paths move together. A technically complete build can still fail if the organisation cannot adopt it safely.