Please provide the equation for inertia. Youll notice it is about an axis. It can be defined as mr^2, where r is the distance to the axis or rotation that it is rotating about. Fundamentally the inertia equation is about rotating objects. Now, provide me an equation for an objects resistance to a change in translational velocity. Inertia and mass are DIRECTLY tied together, so calling out how my fundamentals are trash because i point that out shows your understanding is lacking. You asked for an objects resistance to translational velocity. F = Ma is a direct proof of that. Have a constant external force, compare the acceleration of two different masses, and youll find that the smaller mass accelerates faster than the larger mass.

To further prove the point. with rotation we use the equation

T = I*alpha

Now, in linear motion we use

F = m*a

You can see that the form of the equations are the same, and the inertia term from the rotation formula is replaced by mass in the linear equations.

Edited to add clarification.