Let's be real here: A ton of work is going into this stuff.
How many people do you think play Overwatch every day? Support covers customer support, crunching numbers on stats, analysing feedback from competitive games, dealing with cheaters, and all of this before we get into the gameplay team taking all that work and implementing changes, additions, and improvements which are then playtested over and over before being deployed.
For the Summer Event they have a brand new weekly brawl mode. People had to design and model the new map. They had to implement custom rules to nake the mode work, and they had to test it to find the right balance. All this just for a few weeks of free distraction for players.
The Summer items? New models for a few of the skins, really nice new animations for the emotes and intros. It's not cheapvto make stuff like that.
Could the lootboxes be handled much better? Sure. Is there a business reason overriding consumer benefit? Yes, definitely. Is Overwatch content cheap and low effort, costing next to nothing to produce and maintain? Lol no.