The Missal directs the people to strike their breast once during the Confiteor of the Penitential Rite, and to make a profound bow (of the body, not just the head) during the Creed at the words you mentioned. Just because most people (and even priests) don’t is no excuse to abandon the practice.
(Also, on the Solemnity of the Annunciation – coming up on March 25th – and on the Solemnity of the Nativity – you know, December 25 – the proper posture during those words of the Creed is to genuflect, rather than simply to make a profound bow.)
You should do these things. Perhaps by you doing them, other people will see them and do them too. Better yet, perhaps they’ll ask you first why you’re doing them – and hopefully you know WHY you do them – and you can catechize them briefly and then their active participation in the Mass will be enriched.