But it should knock prone as an option as well. That's one of Shove's biggest abilities. Take that away and reduce to 5 feet, and I agree, a Bonus. Do Shove right and allow to knock prone and ot should be an Action.
I'd find a perfectly acceptable compromise if it would spare us the choice between the "option" and just merged the two functions in one: knocking people prone AND five feet away. You would still have the option to push people down a cliff (IF they were on the edge of it where it made sense).
Anything is better than having it as a bonus action AND the equivalent of a trebuchet (bordering into the intercontinental missile), by capable to throw people kilometers away.
Also, if it's not too much to ask, we could have that enemies falling down would... you know, fall down, instead of flying horizontally for meters in the best Wil E. Coyote tradition.