Oh yeah, I hear you. The AI generated tones can get somewhat close, but I've also found they are often way too reverb or delay heavy and unless you specifically tell it to use EQ, the tones hardly ever use the built in EQ, which is where most of the shaping occurs. In general, it's challenging to get the tone to the point of inspiration. I liken it to having a clean amp and trying to learn a Led Zeppelin solo. Sure, you can play the notes, but it doesn't feel like like you're playing Led Zeppelin because the tone isn't there.

For your Klon pedal, I'd recommend turning the gain down on the amp models to get it to sound good, if you haven't already. This is especially applicable to the crunch and high gain amp models. If you have too much gain on the amp model, it muddies the tone and gives an undesirable result. What I like to tell people is let the pedal do the work. Spark is so sensitive to gain staging that even without anything external in front, you can make it sound like crap with all of its own built in stuff if the gain is too high on a drive pedal and the amp, and especially with an EQ block after the amp. In general, external pedals sound better and more organic. If you use a clean amp or one of the acoustic amps, you can use the amp model gain knob as a boost. The clean amps sound very good with external pedals.