A lack of analog controls is definitely an issue. Having digital buttons on keys that are either 100% on or off loses a ton of fine control.

Playing GTA and need to make a slight left while driving? On a gamepad you just slightly tilt the stick left to make a smooth turn. On keyboard you have to do a bunch of short little taps on A (and D when you inevitably oversteer) to stop yourself from jerking the wheel left.

I remember really wanting a Logitech G13 when they came out but I could never justify spending the money on one.

For movement I would take something like a HOTAS over keyboard. For example in games with multiple movement speeds finding the right speed is rather cumbersome on keyboard because the key press is an on/off and not a scale.

Similarly on keyboard movement is restricted to 8 directions. If you need to move in some other direction most people actually use a mouse to compensate for the lack of movement options because it's too cumbersome with a keyboard.

There are benefits to using keyboards but there are places where you can use something better. Analogue input simply gives better movement options.