Were it not for the teeth it would be a safe bet megalodon was a filter feeder like the largest extant sharks. But dem teef! If it were preying on more reasonably-sized things one would assume it would have more reasonably-sized teeth–proportionately bigger jaws given its overall length, maybe, with (lots more) teeth about the same size as a great white’s to work the same kind of prey. I mean, the maw is so big it wouldn’t really need to even bite a seal or a salmon, or even a tuna if it could catch one, so no need for teeth at all. They had the gear for biting whales, especialy if they could extend their jaws the way the goblin shark does (freaky youtube videos readily available).
Is it possible/suggested they competed for carcasses, perhaps tongueless baleens, and so would need to be able to excise a huge mouthful, quickly, and then chomp it up at their leisure while staying out of the way of other competetors? But does a scavenger NEED to be that big? Seems like you only get that big if you need to overpower something, otherwise you stay worm-sized and numerous. That’s not really what the OP was asking though.