mosfet gate follower
The circuit has more serious flaws than slow turn off. First of all, it doesn't turn the FET on completely. Depending on the threshold voltage, it most likely stays permanently off. The maximum gate voltage from this circuit is about 1.8 V, with no drain current, reduced by the sense resistor voltage drop.
You should at least supply undivided 5 V to the gate, if it's a logic level FET with a low threshold voltage.
Faster turn off may be achieved by a push-pull gate driver, may be advisable for a high switching frequency.