Take stock of what happens outside the system
List the spreadsheets and manual tasks that complement the ERP. Ask what need each one meets. Some exist because a feature is missing; others arose from a lack of knowledge, unsuitable permissions or a configuration that stopped being useful.
Check the options in your current system
Review with the technical owner which needs can be addressed through configuration or integration. Distinguish maintainable changes from customisations that complicate upgrades. Request a scope and estimate before comparing with a complete replacement.
Include the cost of organisational change
Migration involves more than transferring data. You need to prepare the team, check reports and define how the systems will coexist during the transition. Compare that effort with improving the current solution and document the limitations that would remain.
Make the decision using verifiable criteria
Define the results you need and how you will test them. If the current system cannot meet essential requirements with a reasonable level of effort, you will have a clearer basis for assessing alternatives.