Double checking the dates. CVS is 1990 (source control before SVN before git). Visual Studio first release is 1997. Eclipse and IntelliJ are both 2001 one month apart. PyCharm is 2010. Jenkins CI is 2005 (initially named Hudson). Teamcity is 2006.

Code quality is limited to the tools available at the time. It was an uphill battle to preach for (automated) scripted builds or any form of (automated) testing without having the later tools/frameworks/infrastructure at disposal.

Funfact: The java compiler was still fixing "bugs" in 2016 to be able to produce an identical JAR between builds.

Nowadays if an intern opens PyCharm. He can get right away a lint report on the current file and entire codebase, finding potential bugs and questioning why is this thing not running automatically on commit. This pushes quality up organically quite a bit. By comparison doing embedded C++ development in the 2000's, I can only recall of one company having a static code analyzer, that costed no less than $50k for a handful of small projects (they charged by line).

I can't really blame them for nondeterministic builds. Not only was Java slower but computers in general were slower when javac was written, so recompiling unchanged source files was an obvious waste that everyone tried to avoid (by checking mtimes, because hashing every file was also pretty expensive).

I doubt very seriously that Amazon was running on Windows servers so I fail to see the relevance of Visual Studio. Even so, the first version of Visual C was released in 1993 (https://winworldpc.com/product/visual-c/1x).

C is not a new language. People have been writing large well structured C code for decades. The first C linter was written in 1978. Even PC-Lint was written for C in 1985.