Do you want buyable loot boxes or having to pay for characters, maps, and modes?
That's a false dichotomy, loot boxes are certainly not the only way to monetise the game via micro-transactions and the alternative is not paid core content.
It's good in the sense that, as someone who doesn't intend to buy loot boxes, I don't feel like I'm at a disadvantage in earning skins. Allowing people to buy individual skins would make it more attractive for people to spend money because you're getting the "advantage" of being able to pick the skin you unlock. If you get loot boxes through the normal course of the game, you don't get to pick; you get skins at random. As a result, that system would incentivize gamers (who are already buying the game mind you) to spend cash as it provides an advantage in earning skins.
If you can only buy loot boxes, I don't feel any more incentivized to spend money. Purchasing them doesn't give any advantage other than speeding up the time it would take you to earn more loot boxes. It provides the purchasers with the chance of getting the skins they want sooner (and more than likely earning enough credits to buy whatever skin they want), while not providing an unfair advantage that aims to incentivize non-paying users to buy into the microtransaction system.
Buying specific cosmetics may make it more attractive for people to spend money, but thats because its a more attractive option and more importantly fairer to the consumer. Blind buying a random selection of items with various rarities (and even worse, no guaranteed rarity distribution) is pretty explicitly anti-consumer, just like it is in every other medium its used in. Talking about which offers a better incentive is missing the main point, which is, which offers a better return on money spent. Let's say I want a Mercy skin, if they were selling cosmetics I could pay, lets say, $10 to get it, with the current system I could spend $50 or $100 and still not get it or the credits to pay for it. Offering customers a good return for money spent may be an incentive to spend money, but generally a much smaller amount. Enticing people to gamble offers the publisher a steady return, especially for people who have an issue with it, while offering the consumer a terrible return on money spent.
Ultimately it is what it is, Blizzard arent going to change it and people who arent going to spend money wont and will get the content for free (which is what I intend to do as well, so no moral high horse here). But I certainly dont think it's a good system or one that should be applauded.