To get someone to take a job, they must believe it is a good job for now and either:
- Truly believe it will be a good job for the rest of their working life
- Or believe it will not stop them from getting their next job
As no one can predict the following:
- how long a company will be in operation
- whether the company will be bought over and/or the work moved to another country
- whether the employee will be forced to leave due to a bad boss
- if an employee wishes to relocate due to a relationship etc
Most people are sensible enough not to believe a job is for life, unless they are only planning to work for a few more years.
The bottom line is this. Most employers expect people with up-to-date experience in the systems they are using... hence there is nothing you can do to attract and retain candidates, without giving them some work on modern systems.
Therefore you may need to take on additional projects that allow you to train all staff in modern systems and give them the experience while having them spend a few months a year on the "outdated" technologies.
Or maybe you can become the best employer in town for training, with everyone knowing that when someone has worked for you for a few years, they can get jobs with lots of other companies. You can also offer flexible contracts, free workplace childcare, part time work arrangements, the list goes on. Essentially making you the only employer in town that fits well with some peoples' lifestyles.