The animation in that era of Dexter's Lab wasn't even that bad either, sure it's different and a bit basic, the backgrounds in the third season may have been a bit lazy but it was UPA inspired. Not just that but it was the style at the time as geometric shapes were the dominant style of the 00s (ie Fairly OddParents, Billy and Many) You also can't fault them for switching to digital ink and paint, due to how quickly technology was progressing during that time period. Clone High had the same style as Savino Dexter (I read somewhere that this was due to them having the same designer) yet it's praised for it's angular style.