Shove can either move a target 5 feet away or to knock the target prone. Both of these are useful, but not overpowered, since it takes an entire Bonus Action to achieve this in addition to using your Action to Attack.
If you shove target 5 feet away then they are now out of range of any opportunity attack against you, unless they have a reach weapon. Your archer allies can now fire at them without the +2 AC for being in combat. You could have done something similar by taking the Disengage Action and using your Bonus Action for something else.
If you knock the target prone then you have advantage to attack them (if you have any attacks left this round) but all your archer allies have disadvantage to hit. Your target can still attack you (including opportunity attacks), but at disadvantage.
In any case, the foe can stand up or move on their next turn, meaning shove is of less use the fewer PCs have their turn between the fighter and the foe.
Shove is not automatic though - the target gets an attempt to resist, using the best of STR\Athletics and DEX\Acrobatics. Sadly, very few foes have STR\Athletics proficiency and even fewer have DEX\Acrobatics.
I do feel your frustration though. My fix for this issue has been to give Athletics proficiency to foes I feel really should have it. For example, animals associated with strength (gorillas, bears), martial foes (bugbears, hobgoblins, devils). Not every foe, though - we have to give characters the chance to shine and feel badass.
Also, what do you mean "low-level fighter?" A +7 on STR\Athletics means a Strength of 20 for a level 4 or lower Fighter. That is not easy to get. A bard or rogue would still struggle to reach +7, as they would have to have Strength 16, unlikely for those classes.
Short answer: Shoving is situational, not overpowered.
P.S. elephants are huge creatures. Unless your bard is a giant, they are not flinging elephants around.
