I worked for a retailer for many years that had a bespoke system that ran the business. It had been designed and built to meet the exacting needs of the business. Isn’t that what gives a company a competitive edge, as it doesn’t work the way everyone else does. Large scale legacy replacement projects (often) have a high risk of project failure.
It was considered old fashioned and outdated so a very expensive ERP solution was purchased costing millions, then the company spent a fortune having it changed to work in a similar way to the way the business currently worked.
If the business had spent half of the amount enhancing what they had they would have been in a better place. To this day I don’t know why that decision was made other than I am sure those who chose it thought it would look good on their CV.
Needless to say, the business is no longer around!
Other options
If you have a legacy system that has reached end of support it’s often possible to negotiate a support agreement. In some cases, it’s possible to purchase the source code from your vendor.
Holding back also has its advantages; the longer you wait to replace your legacy systems, the more up to date your next system will be.
If you currently have a system from the 1980s. If you replaced it in 2005 — you might have chosen a technology based on a technology that is no longer in favour and you might be looking at having to replace it again. If you replaced it today you’d have better technology choices.