There are three perspectives when determining if a solution is a fit for purpose.
The first perspective is business functionality. Does the solution provide the business functionality required? Where the solution does not provide the functionality are there workarounds such that business can complete their functions. A key aspect of this perspective is the resource that will be using the solution. Are they willing and able to use the functionality the solution provides?
The second perspective is the data. Is the business data being stored in a way that makes it usable both for the solution as well as any downstream processes including reporting? Data is a key business asset and if the solution does not provide capabilities for handling and storing the business day the solution may not be a fit.
The last perspective is support. Business constantly changes and the solution needs to adapt with the business. The support that the solution provides for changes, bugs, and training is key for determining if the solution is a fit.
Each of these perspectives provides value to the business. The cost of the solution in relation to the value the solution provides encapsulates the fit for purpose decision.