In my experience, pen raised gamebird meat of any type tends to taste pretty close to chicken...at least compared to the taste of their wild counterparts. I've had pen raised chukar and I can confirm, it tastes pretty much like chicken. Never had a wild chukar so I can't make an accurate comparison there I suppose. But pheasant is the same way....and I've eaten plenty of both wild and pen-raised pheasants. Pen birds might as well be chicken. Wild birds definitely have more flavor. Similar to chicken but much tastier I think.
Diet and activity level contribute to the difference in taste. The fact that you fed "chicken feed" rather than gamebird feed isn't the issue...it's all the same basic stuff. Rather, it's because the bird ate a consistent, clean, balanced, corn-based diet its whole life and there's nothing in a commercial diet that would lend a strong flavor to the meat. Just like the taste difference between free-range meat chickens and confinement raised grain-fed meat chickens. The varied diet of a free range or wild bird lends a different flavor to the meat. Taste can even vary from bird to bird, depending on the individual bird's main habitat. A soggy swampy pheasant that was hunkered down in a muddy slough usually has a stronger, almost murky taste to the meat (and they usually stink to high heaven when you clean 'em)....whereas a pheasant who has lived next to a corn field all year will have a cleaner, milder taste.
Activity level makes a difference because, well....muscles are meat...the more heavily used the muscle, the darker the meat & the stronger the taste, generally. All the meat on a wild pheasant is about the same color.....a shade somewhere between white & dark meat on a chicken. Pheasants run as much as they fly, so the legs and breast muscles get the same amount of use & are close to the same color. Pen raised birds that aren't flight conditioned will have much lighter breast meat and darker leg meat.
But yeah. You're not doing anything wrong cooking it, pen chukar is pretty much going to taste a lot like chicken no matter what...unless you want to build a flight pen, let 'em free-range and go out once a day & make them do flight aerobics?
