Most companies where I worked have a history of rebuilding their applications every 3 to 5 years, some even 2 years. This has extremely high costs, it has a major impact on how successful the application is, and therefore how successful the company is, besides being extremely frustrating for developers to work with a messy code base, and making them want to leave the company. A serious company, with a long-term vision, cannot afford any of it, not the financial loss, not the time loss, not the reputation loss, not the client loss, not the talent loss.

If I can find some time, maybe I can help pitch in somehow.

That should work, but it's a non-trivial change.