This isn't only evident in the use paid currency to purchase items and gacha mechanics and publication of drop rates of rarer items. Gacha refers to using game currency, whether it's free, or purchased through an in-game shop, in order to get something you want like pieces of D2R Items equipment for instance, in the case of Dissidia Final Fantasy Opera Omnia, or characters in the ever popular (and ever-lasting) Fate/Grand Order or Genshin Impact.
In the case of Diablo Immortal, there's the usage of legendary crests (which can be obtained or bought) to increase the chance of a 5-star gem appearing in the dungeons and dungeons endgame. Although it's not exactly traditional in its way of presenting (most gachas are played out by "rolling" using a time-limited banner) the players are engaged in the same kind of randomness in a similar manner. In many ways this is how players are engaging in the same way. Diablo franchise was building towards these mechanisms since the beginning of its existence as Maddy Myers wrote a few weeks in the past.
D2R also, in clear terms, draws direct inspiration from the "feeding" method that a lot of Japanese, Korean, and Chinese mobile games have used for more than a decade. "Feeding" is the process of increasing the attributes, stats, or rarity of an item through getting a duplicate of a drop. The duplicates then feed to an item with similar rarity, which increases the overall stats for the item. Generally there are five copies as the industry norm to max out a character or item.
My first experience with "feeding" was through Fate/Grand Order, which was first out on Japan in July of 2015. It grossed a total of $4 billion dollars globally in the year 2019. To ensure that a character is the very best possible I had to purchase copies of each. If a certain banner came along I was able to pay more than 300 euros for the character I had coveted since a long time. But I didn't get the duplicates I needed to realize the full potential of this character. The rates for the most valuable 5-star characters now sitting somewhere at 1%, it was no surprise that I didn't manage to acquire a replica of the character when I was engaging in this game (which I've since deleted). In July 2021, Fate/Grand Order was the seventh highest-rated mobile game of all time, and was ranked ahead of Konami's Puzzle Dragons, which could be added to the list because it is also a gacha-based game.
During an GDC 2021 speech, Genshin Impact developer Hoyoverse (previously Mihoyo) outright admitted that the method used to create characters was based on generating the most capital possible from its customers. For example, the Raiden Shogun and Diablo 2 Resurrected Ladder Items Kokomi character reruns in March 2022 alone earned the company over $33 million in revenue.