I've dealt with many nasty rendering bugs in chromium that were never addressed, from weirdness that just made rendering a bit ugly, to spec-incompliant layout (that also differed from other engines), to iframe-related stuff that left half of the frame completely white, to animation/transition related gotchas, to outright renderer crashes, including some that brought down the chromium wrapper process (which may have been security risks, but figuring that out isn't easy). And ditto for firefox. This is years ago by now, but my impression isn't that chromium doesn't have bugs nor that it fixes bugs promptly, but rather that all websites and web-toolkits necessarily are designed with chromium limitations in mind. That's certainly what I did - no point in releasing anything that doesn't work on chromium; that'll just get you laughed at and ignored.

The chromium bugtracker too is full of ancient unresolved bugs, just like gecko's bugzilla: https://bugs.chromium.org/p/chromium/issues/list?sort=id, and I'm sure that if you wanted to you could find a ton of decade old bugs that leave you wondering how those weren't fixed by now.

This just seems to be a fact of life with various browser engines. There are surely all kinds of more or less reasonable motivations to ignore those old bugs, but whatever the cause it's certainly the status quo.