I mean that while Netscape, the company, succumbed while waiting to put out their new competitive browser, we now have the Mozilla Foundation and Firefox.

We wouldn't have those if it wasn't for the rewrite. The old code was a mess even before version 4 (by its developers own admission), and it could never get to the point of competing in the engine space ever again.

That is, with the old Netscape rendering engine it would not be possible to extend it to compete in the modern HTML5/Canvas/GPU acceleration/CSS3/add-ons/separate contexts for each tab/etc era.

And since we are talking here more about technology, and not business models, we should more or less regard the Netscape rewrite as a success story. They did NOT produce a system that was over-engineered or that failed to perform well. Indeed it took a tremendous amount of market share. Now of course they complain about the code again but the situation is far from desperate.