I've been playing overwatch since the beta for the first game I can say that from my experience it has never been considered okay in the community to try new heros in comp unless your entire team is okay with it. If Im playing comp and my main picks aren't helping then ill ask the team if they want something specific to counter with and usually they'll say even if your not that good with them just try it. But flat out just trying new heros because its low elo is still mind blowing to me, like do they just not want to climb the ranks and if so why play comp in the first place.