Verilog Netlist and verilog file not justifying each other
The output only depends on enable and in[0], resulting in the following coding optimization:

module test (input in, input enable, output out);
assign out = enable &amp; in;
endmodule


where in is the old in[0], and the output has been changed to a wire type. Normally, a synthesis tool would do that optimization for you, but here it clearly does not. Optimizing your code yourself will make a circuit which is just one gate instead of 3 gates as in your current result.

I drew the schematic of your netlist and there is not enough information to know if it matches the RTL. I would need to know how the MUX4 module maps the inputs based on the select signal. You can see the "??" which represents some combination of in1 and in[0]. But it is not known which combination selects which input, since you didn't attach the MUX4 model.