The thing is, Lynch never wanted to solve who killed Laura Palmer. I've read countless bits with him where it was all about process and drawing things out and going on story detours, that the Palmer killing was the invitation into TP, NOT what the show was actually about at all.
I think the dynamic between Lynch and Frost was a very good one, but that it got out of balance when Lynch was away shooting a movie. I think Frost's notion of the Black Lodge is a lot more interesting and textured than what we get from Lynch, which seems more B&W. Then again, the next time I watch the last ep, I'm sure I'll reverse that opinion (the series almost never plays the same way for me, which is how I manage to rewatch it every year or so.)
And based on stuff that was in WRAPPED IN PLASTIC magazine, the finale was a bit clearer as scripted, and Lynch definitely weirded it up a lot, which is good in a lot of ways, but still kind of pissed me off at the time (not as much as the killing of another character a couple shows before the Palmer wrapup, which practically had me kicking the TV in I was so enraged.)