Comparing the bond strength between a polar bond and non-polar bond According to NCERT class 12 part 2, $\ce{ICl}$ has lesser bond enthalpy than $\ce{I2}$. I have read that non polar covalent bonds are weaker than polar covalent bonds as in polar covalent bonds partial opposite charges develop on the bonding elements which leads to extra electrostatic interaction between them which is absent in non polar bonds. So according to what I read the answer should have been opposite. Please let me know where this logic is wrong. Also using this logic I understood that ionic bond is stronger than covalent bond.
In polar covalent bonds, say $A–X$, assume electronegativity of $X$ is greater than that of $A$ then their is polarisation of bond $A–X$, $X$ gains partial negative charge $\delta–$ and $A$ gains partial positive charge $\delta+$ but this charge is very less (as electrons of sigma bond are held tightly) to account for any significant increase in bond strength of $A–X$ bond but the $–X$ group in $A–X$ molecule tends to attract $A–$ group of another $A–X$ molecule in this way there is electrostatic interaction between two different $A–X$ molecules giving rise to intermolecular forces (Dipole-Dipole interaction, hydrogen bonding etc).

DO NOT CONFUSE
FORCES BETWEEN TWO DIFFERENT MOLECULES AND COVALENT BONDS WHICH EXIST IN A SINGLE MOLECULE. THEY ARE TWO COMPLETELY DIFFERENT THINGS

However, attraction or repulsion may exist between two parts of a single molecule (generally happens for organic  molecules) but doesn't significantly affects bond strength between them rather they tends to change orientation of those groups or may rotate about the sigma bond.

And for $ICl$ and $I_2$, bond of iodine and chlorine is weak due to polarisation. And bond between iodine and iodine is strong covalent bond. I hope you know that polarisation of electron cloud of sigma bond decrease overlapping between orbitals.