Legacy code is called legacy for a reason. It works. It's been tested in production. It's often the most reliable code in your system, even if it doesn't follow modern conventions.

The idea that frameworks solve problems is mostly marketing. They shift the nature of the problems, making some things easier and others harder. The trick is choosing the right tools for your constraints.

Related

More on this topic

APIs are contracts. Once you publish one, changing it becomes expensive for everyone who depends on it. The cost of breaking changes compounds over time, which is why the boring, conservative choice is usually the right one.

Understanding the problem is half the solution.

APIs are contracts. Once you publish one, changing it becomes expensive for everyone who depends on it. The cost of breaking changes compounds over time, which is why the boring, conservative choice is usually the right one.