Gain deficit and phase margin at crossover
The control-to-output transfer function of the CCM buck converter operated in voltage-mode control is that of a 2nd-order system. The small-signal equivalent model is shown below:



If we determine the control-to-output transfer function using fast analytical circuits techniques or FACTs (how a stimulus on \$V_{err}\$ propagates and forms a response in \$V_{out}\$), we should find:

\$H(s)=H_0\frac{1+\frac{s}{\omega_z}}{1+\frac{s}{\omega_0Q}+(\frac{s}{\omega_0})^2}\$ with:

\$H_0=\frac{R}{r_L+R}\frac{V_{in}}{V_p}\$, \$\omega_z=\frac{1}{r_CC}\$, \$Q\approx\frac{1}{\frac{Z_0}{r_L+R}+\frac{r_C+r_L||R}{Z_0}}\$, \$Z_0=\sqrt{\frac{L}{C}}\$ and \$\omega_0=\frac{1}{\sqrt{LC\frac{R+r_C}{R+r_L}}}\$

If I now capture these data in a Mathcad sheet, the results you want at 5 kHz (assuming the minimum input voltage of 10 V and the maximum output current) are given below and are close to what others have found: 9.1 dB of attenuation and a 146° of phase shift: