A few decades ago when the human genome was first being sequenced, it was assumed that most genes would have a straightforward 1:1 relationship with specific associated traits (so you’d find a “gene for X” and a “gene for Y”). And while there are a few genes like that, it turns out that most genes are part of complex gene regulatory networks that resemble neural networks in that there are complex non-linear relationships between the inputs and outputs. So if you want to make a specific change to a specific trait, you have to edit multiple genes, and each of those genes affects multiple other traits you weren’t intending to change, etc.