You're talking about a professional software suite meant to work on workstations often solely meant to run that suite.
Chrome has to cooperatively share resources with other applications and with aggressive caching at application level, the only strategy at hands of the OS is to start swapping.
I'm responding to the assertion: "The OS should use all available RAM it practically can for things like cache.
Not the applications."
Applied absolutely, it results in deeply sub-optimal behavior in a large number of cases.
Another case could be image decode caching via glide for scrolling lists, or skia output tile caching in a browser, or texture caching in a game engine, or reference frame caching in a video decoder, or glyph caching in a word processor, or block caching in a constructive solid modeller, or result caching in a spreadsheet, or composition caching in a presentation tool, etc. etc. etc.
Caching is an enormously effective tool for applications and operating systems. If an operating system removed it as a tool for applications, it wouldn't likely be a competitive operating system.
Should applications abusively and single-mindedly monopolize memory usage? In some cases, maybe. In general, I think we'd tend to be on the same side of things. I like to see well-behaved applications (that make conservative and efficient use of system resources) and robustly managed operating systems (that don't let apps walk all over them).
Chrome has to cooperatively share resources with other applications and with aggressive caching at application level, the only strategy at hands of the OS is to start swapping.