"Is it forcing us to "pay off" technical debt or is it starting us on a compulsory endless treadmill of feature-neutral fix-work? Collectively, we just won't know for a while."

Yes, let's fix the foundation. It will make adding features easier once the debt is paid off. And we will probably learn how to do better in the future. It reminds me of settings compiler warning to be treated as errors. Once you do that, you have a ton of work to do. But if you are smart (not all devs are), you learn why the warnings are there and avoid these problems in the future.