My definition of C&W is simplistic and ahistorical: Prominent acoustic guitars, more major than minor chords, lyrics that deal with real, clichéed or perceived life of the "simple folks back home", songs that regularly clock in at three or four minutes = Country (enough) to me. You don't have to share DNA strains with Hank Williams or Loretta Lynn.
Rucker isn't any less Country to me than Keith Urban, Zac Brown (his band has even a lot more rock elements than Rucker's current music has) or Garth Brooks and more so than country-pop tinged bands of the past such as Loggins & Messina or Firefall. But it's probably a question of perception, from our side of the pond bands like The Eagles, Poco and America were always referred to as Country Rock and the borderline to real Country back in the 70ies was basically whether you had long hair as a man or not and/or did the little yodles and yelps in your singing or not. If Garth Brooks hadn't had short hair and if he hadn't yodled, then "New Country" would still be Country Rock IMHO.
If Rucker moved to Jamaica and recorded a reggae album that was any good I wouldn't hesitate to call him a reggae artist. I don't work myself in a state how true someone stays to the origins of a form of music (or whether he/she originally played it) as long as he/she does it well. Rucker played indie-pop-rock (with an audible country tinge) with Hootie & the Blowfish, he now plays (New) Country (pop) that retains some connections to his musical past. His voice is more white soul/rock soul than country, I grant you that (Edith thinks he sounds like Eddie Vedder), but otherwise he sticks pretty much to the Country script. And not every male country singer has to yodle!!! And Frau Crow once surmised very aptly when questioned why she had "suddenly turned Country": "Well, if you really listened to my music, it was always there."
But before the C&W Thoughtcrime Police gets me, I'm happy to discern from now on between "Country-Country" ("Köuntry?") and just Country!