Masks and procedures are effective but not 100%. I was religious about masking and distancing and hand washing and still got Covid Original Flavour(tm). Fortunately, I did quarantine after getting back from my travel (required: had to shut a house down) before even knowing I had Covid so my elderly relatives didn't get it from me.

Quarantining is very effective but is really inconvenient. You can't get every single person who wants to interact with you to quarantine for 14 days prior unless you are super important.