It did feel like a TF clone initially and that's what put me off the purchase. But while I really disliked TF2, I love Overwatch. Feels a lot more polished and pushes towards co-ordinated team-play. Flanking is encouraged but it's in a tight window or still being proximal to the objective. So it's corridor, but wider than that - and generally results in a lot of fun.
Blizzard does rip off other ideas, but when they do, they generally do an as good if not better job.