You can get protein toxicity from any meat, and it's not a concern unless you're starving in the middle of winter and have literally no food besides meat.

Also, ancient people didn't have factory farmed broilers, and millennia of selective breeding for meat, those chickens were lean as well.

The males are exceptionally aggressive as well...

Because cocks are gentle and don't regularly attack humans? And that's after a lot of selective breeding to make them more docile, and not for fighting.

Duck eggs are not for everyone. And the creatures require more water. The fatty meat is not very agreable for everyone.

Edit: Apparently they were domesticated a lot later.

Yeah guinea fowl were a stretch for many reasons.