What am I doing wrong with melee mechs?

I see the tooltips say "will stagger enemies", I get hit by other people playing this mech and it staggers me, but when I play any melee and hit enemies they take a single hit and get away without even trying. It seems like I can never stagger enemies outside of very clearly dedicated moves like panthers charge or stellaris' grapple. I get there's antistagger abilities but this is every single character all the time no matter where or how I hit them. I must be doing something wrong but I dont know what.