Netscape's demise was completely due to the mismanagement of the company, not the particular features they provided. In the middle of the browser war they decided to stop all maintenance and execute a complete rewrite. That would kill any company. They are one of the reasons why Joel Spolsky says "never rewrite from scratch".
And I'd suggest that "don't stop and rewrite" is not the important lesson. It's "don't let your code base get to the point where you have to stop and rewrite".
Netscape's rewrite was 1997-2000. In 1999, Martin Fowler published "Refactoring", which showed us how to continually improve the technical architecture of a system without trying to stop the world. JUnit, the first really popular testing framework came out about then as well; good unit testing makes it safe to refactor boldly. And the Internet itself gives us the ability to release early and often, encouraging us to do everything in smaller, more manageable chunks.
Giant rewrites were just what you did in the bad old days. But we never have to do it again if we make a point of keeping our technical debt low and our releases frequent.
