Doesn't Chromium use its own font rendering system?
Not really. It has to do a lot of font-related work to implement the web standards but they're using freetype2/harfbuzz like everyone else.
I've noticed that on other OSes it has its own rendering style that doesn't use subpixel rendering either, so it looks different but not necessarily worse.
You're getting confused by the fact that it didn't use DirectWrite on Windows for quite some time. It *certainly* had subpixel rendering there and on the other supported platforms. Windows has both a legacy font rendering stack and a modern one with a different appearance and better performance. Many applications use the old stack but people spend a lot of time in browsers so it got noticed.
It looks fine on my Arch install, so its either respecting my font settings or the in-built rendering settings are (perhaps by coincidence) the same as my own preferences. I should point out that I always turn off subpixel rendering and use greyscale antialiasing instead, because the colour fringes on subpixel text are annoying.
I doubt you're able to notice color fringes with black-on-white or white-on-black with the lcdfilter set to lcdlight. You probably just didn't have it configured correctly (i.e. no lcdfilter).