Talk is cheap Adam until you've done at least one major enterprise grade migration. In some cases, older applications corporations bought have no replacement or alternatives. Heck, I've seen old mainframes with legacy applications still being utilized to this day.
Others, well we are talking custom multi billion dollar applications here. This is not your Microsoft Office. This is not something you can get off the shelf off Amazon.com
You literally are starting from scratch. Corporations have to:
- Conduct feasibility studies and put together proposals
- Have Business Systems Analysts to Perform JAD Sessions to gather requirements
- Get upper management to approve the investment
- Investigate Rules, and Compliance and integrate those requirements into the application
- Code/Program the Application
- QA The Application for Bugs and Security Lapses
- Fix bugs and QA as appropriate
- Train Employees on How to use the application
- Develop Translation Applications to interact with the legacy databases OR create importers to import the data into the new application
- QA that translation application or importer
- Setup test environments to test the translation application/importer on copies of production data
- Do multiple dry runs in a test environment to determine and isolate any issues when doing the actual implementation.
- Design and setup business continuity/disaster recovery plans.
- Implement BCDR plans.
- Perform BCDR Drills.
- Perform the implementation
- Support the application answering questions for employees on how to perform certain actions.
Each of these above steps is roughly anywhere between 3-18 months in time. Assuming the above 17 items I listed took 6 months, that's about 8.5 years roughly of work there. And if you have not noticed, the economy is in pits and companies are not exactly lining up around the corner to spend money on new application development.