Technology has certainly come a long way. On that we can all agree. Many changes in the IT landscape are helpful and involve better performance, flexibility, or new features. However, as most experienced IT folks have learned, not every feature is useful and sometimes the upgrade is a not good idea.
Many concerns around stabilizing or ring fencing old environments are related to security, supportability, or getting better flexibility can be addressed without ditching and starting over. In some cases, even an upgrade is not needed. There is an old saying by Upton Sinclair “It is difficult to get a man to understand something, when his salary depends upon his not understanding it!” Of course your operating system vendor insists that upgrading is 100% needed. Of course your database or application vendor insists that an new version is necessary. As if they'd ever say the opposite!