Grabs are super low priority so they shouldn't be a plan A offensive tactic unless you're using one of the characters with a kill thorw and it's time. Generally you want to grab in one of two situations:
-Grab is the overall best punish you have in the current situation. For most characters, landing a grab is somewhat better than landing any tilt but clearly worse than landing a smash; these situations happen a lot especially since you can grab directly out of shield (shieldgrabbing is a big tactic).
-You're specifically predicting your opponent is going to sit on shield. This is easier to do against some opponents than others, and it's more about the player than about the match-up.
There are all kinds of other uses you can find for grabbing (it's useful all around!), but these are the main two situations you should really be looking for grabs. Outside of them, your prime goal shouldn't be to "use more grabs" since, offten, you can do even better with other attacks that control more space and do more damage, and it's not any better or worse to build your damage with grabs or ordinary attacks.