It's pretty intuitive and presented well, but it sure is difficult.
I often felt like I would just lose attempts to pure RNG of pipe selections. The maps are super open, which should make creativity in pipe placement really easy, but I often just did a lot of sluffing pipes that I didn't need while waiting for the pipe I wanted to show up in the queue. I actually think that maps that feel more restricted in terms of space to sluff off pipes might get players thinking in terms of using pipes in places where they could "potentially" be useful if the queue ended up giving them the right combination rather than just dumping stuff in the corner.
I don't know if you've already got some level of logic behind the pipe selection for the queue, but this does feel like a great opportunity for "controlled RNG" that appears to be random, but somehow always guarantees an adequate set of pipes to complete the puzzle or somehow tracks the current build of the player so that it can throw in the pipe that the player is looking for with only limited time left before failure. Just thinking of ways to toss players a bone for the sake of letting them feel less like they lost to RNG and better be able to point at something they personally could have done better during their play.