Random advice from the internet.
If you look at business software, think it is crappy, and wonder why people use it; you probably don't understand the business reasons behind the decision.
As the business becomes more niche, the more likely it is that you don't understand.
But the high level bit is always that the software is incidental to the business, not its core. It is a cost center not a source of revenue. Stable cost centers can be plugged into budgets and cash flow analysis.
Which is to say, "your software is old" is not a business case that will drive sales.
Good luck.
