Poor Rube is always lumped together with Bud Fisher's "Mutt and Jeff" (the long, narrow strip above). Fisher was a funny and creative artist in his prime but he was never as funny, as innovative or as warm and "human" as Goldberg.
Goldberg had more in common with Milt Gross (no example here). Both were funny as hell and both seemed to love the people they were making fun of. I don't know about you but I find Goldberg's bottom two pictures of couples (above) to be extremely tender and appealing at the same time they're caricatured. Bud Fisher couldn't touch stuff like this.
So, is Goldberg's style primitive? No!!! If the purpose of a cartoon is to get laughs then this style is shockingly efficient. The audience is already smiling before they read the caption. If any style can be called primitive it's the modern style (with very notable exceptions), which simply doesn't deliver the comedic goods.