Wait, Overwatch is hardcore? Are we playing the same games here? Or maybe it's because back in my day, the only competitive TF2 was league TF2, where we had teams that you tried out for and sometimes paid money to be on, and map reviews and you'd watch demos with your invite-level mentor so that he could tell you why you suck...
Overwatch, by comparison, boasts a ranked matchmaking system that is slightly less broken than TF2's ranked matchmaking system, but only slighly. Tryhards join this ranked matchmaking system hoping to have serious competitive matches similar to those in TF2's competitive community. The matchmaking system then proceeds to match them with a bunch of complete strangers who are nowhere near the same skill level, who may or may not have a clue what they're doing. None of them communicate, both teams run a Huntsman Sniper, one team stomps the other team, the worst player on the losing team posts in global chat flaming everyone but himself for the loss, the Engineer's sentry gets play of the game and everyone walks away feeling deeply unsatisfied. So basically, Overwatch's competitive mode has all the ballsweat and toxicity of a real competitive community but with only a fraction of the actual competition.
Overwatch also has a Quickplay matchmaking system which does not claim to be competitive or well-balanced. Ever since ranked came out, Quickplay is mainly used for practising new heroes or for pitting a team of six space apes against a team of six emo kids just for the hell of it. The seriousness is on par with that of a Valve public server, but it's still matchmaking, so you still have to wait to play and you don't get choose which map and you may never see your teammates again afterwards, which is a bummer.
They also came out with 3v3 and 1v1 game modes which are almost exclusively for dicking around. Every week they release a weekly brawl, which is a match with some weird rules (imagine a 6s match where you could only play Soldier) and is also just for fun. And every now and then they have events where they release a novelty game mode, which so far has included things like a horde mode and a rocketleague ripoff.
So yeah. IMO, Overwatch has quite a bit to offer casual gamers and not so much to offer serious competitive gamers.