Why do multiplayer games have to cost less then 60 dollars? Is their some unwritten rule? If you think the game doesn't have enough content fair enough, but the mere fact that it is multiplayer only doesn't mean that it can't cost 60 dollars, 100 dollars or even thousand dollars. It's all about what is the value of the content.
Regarding loot boxes, again their is nothing wrong with having microtranascations, it doesn't exploit anything just like alcohol and tobacco stores do not exploit the tendencies of people. Human beings are responsible for their own actions. Also how do you expect the game to still get support today, instead of creating post launch DLC and splitting the player base, the game has microtranscations which do not effect the game at all. This is how the PC market operates, and it is great at doing so. Games get support for years even up to decades, and that is supported by optional microtransactions.
If Blizzard made a campaign for overwatch it would have had to to radically change the development cycle of the game, the amount of content at release, and so much more.
Again their is nothing wrong with a lack of a campaign or with loot boxes if the core game is of value and is good.
That's a flawed example since alcohol and tobacco stores aren't marketed towards children and require proof of age in order to buy stuff. Unless you think selling tobacco and alcohol to kids should be totally legal too because they should be "responsible for their own actions"?
Edit: Also, to add to that tobacco and alcohol clearly say what they have in them. Gambling always shows you the odds of winning and what the possible prizes are. Lootboxes don't, and is another reason they are exploiting people. Much easier for people to decide whether they want to spend money on something if they have an idea what that thing actually is.
And kids do not have credit cards or debit cards which would allow them to buy loot boxes without the consent of their parents, so you can shift the blame to the people who raised them.
Just because betting has odds doesn't mean that it's different then lootboxes, the odds are regarding the payout and are not representative of the possibility of that happening. Just like you don't get a chart on a slot machine in a casino, you're not going to have a chart in overwatch that tells u the chance of getting a particular skin.