Sounds like gentoo has improved their cross-compilation story. I had several attempts at getting a cross compilation toolchain running on gentoo and they all failed. yocto was actually the first time I succeeded at building a cross compiler in any form, but this was a fair few years ago at this point.
To be honest, bitbake mostly seems to be a less principled/polished version of portage or nix. I would much prefer an embedded toolchain based on either of them than dealing with bitbake's syntax and quirks. The one thing that seems relatively unique to bitbake is layers, which essentially mean you can avoid making modifications to the base layer while still being able to patch/tweak just about anything in the build. For embedded stuff, where you're basically almost always working off of someone else's patches to an upstream project which you are then patching yourself, and all of them can update independently, it's the only way of keeping somewhat sane (but the action-at-a-distance can make for difficult debugging, which is something I would wish bitbake was better at: there's no way to query e.g. 'what statement in what file added this compiler flag?', and the set of possible files can be huge).
To be honest, bitbake mostly seems to be a less principled/polished version of portage or nix. I would much prefer an embedded toolchain based on either of them than dealing with bitbake's syntax and quirks. The one thing that seems relatively unique to bitbake is layers, which essentially mean you can avoid making modifications to the base layer while still being able to patch/tweak just about anything in the build. For embedded stuff, where you're basically almost always working off of someone else's patches to an upstream project which you are then patching yourself, and all of them can update independently, it's the only way of keeping somewhat sane (but the action-at-a-distance can make for difficult debugging, which is something I would wish bitbake was better at: there's no way to query e.g. 'what statement in what file added this compiler flag?', and the set of possible files can be huge).