Why is my throttle response so slow?

This sounds as though we have too much free play in throttle system. Have this checked out before running a diagnostic.

In a throttle-by-wire system, looseness or binding of linkage seems less likely than otherwise.... Could it be that your Ford (experiment) is equipped with pedal reach adjusters (for people with average-length legs...yes, that's Ford for you)? Or it could be as simple as miss-planting your feet on the floor board (a problem of late for me due to wearing of an over-sized boot cast due to Home-Depot-crushed toes). Otherwise, because ECM/computer--not you--is doing the throttling, it seems like diagnostic test is in order. You might try probing for problem code if you have a tester; that should "announce" any out-of-range throttle lag or firing delay. I am thinking also that delay due to over-lean mixture could be a "tell" as to an impending emissions test (and cat) failure. Just a thought. Also, what is the weather temperature like when this happens; or is it a persistent problem rather than intermittent? And, yes, pedal anomaly was a "Ford" problem I experienced once during a gradually-degrading-to-failure TPS fault leading to disabled engine.

Regarding your observation about other car makes, I am reluctant to disillusion you but Ford is "famous" for built in faults that don't usually show up in other (domestic) cars; and practically never if "foreign" cars. That true especially for its Fusion-Taurus clones. Their factories have a special nomenclature for avoiding admission of, and taking responsibility for, its engineering blunders: "undesirable but tolerable operating characteristics."

Probably a fuel pump going, clogged fuel injector or clogged fuel filter. Hesitation is always gas related. Without a check engine light I'd rule out fuel injector because that would throw a code for missfire.

See if you can borrow (at autozone or a local parts store) a fuel pressure gauge and hook it up to the fuel rail. It should read over 40 psi, if its lower replace the filter first (its cheap). If not its your fuel pump

See if you can get a code scan. A defective drive-by-wire unit will throw an error code.

A bad Throttle Position Sensor may be cause affect it also(DBW unit usually don't go out too often)...

weird man, good answers by horn and dave tho. possible injectors maybe fuel system pressures to, but id lean towards the throttle cable like horn!