Mobile gaming gave rise to some particularly terrible addiction based mechanics - grind gates, time gates, etc. due to their 'f2p' nature and the evolution of separating players from money. In addition, it created a 'race to the bottom' in price (free, $1, etc) that often rewarded (to an extreme) cloning other games.
Previously, games were 'balanced' for fun and challenge. For example, you need to fight a fair amount of goblins to get strong enough to beat the Goblin King. The developers had a vested interest in making sure the gamer felt the challenge, but didn't get 'bored'. With the advent of mobile gaming and F2p, the games in question are no longer balanced for fun and challenge, but rather, for monetary gain. Sure, you can spend 10 hours killing goblins to earn enough gold s to buy a weapon you need to kill the Goblin King... or you can spend $1 for a 'Green Gem' that will get you that sword instantly. That's intentionally bad/unbalanced game design in pursuit of money, and it is an epidemic and plague on gaming in general.
[obviously, not all f2p games are abusive, but the concept is inherently abusive in terms of general design designs and plenty of games are extremely abusive. The 'wait 5 hours for corn to grow or spend $1' are perhaps the most obvious -- pure addiction peddling.]
Mobile gaming is also so successful (due to the sheer numbers of smart phones/tablets out there, etc) that some of those mechanics have entered traditional gaming, or accelerated existing aspects.
Obviously, some games on Mobile are fantastic. But there are plenty that are both popular and guilty of some of those mechanics.
That's why people 'hate' mobile gaming (well, that and the lack of buttons). And when people say they hate mobile gaming, that's basically what they mean. I'm sure most agree there are some gems, but they are essentially talking about the plague of bad mechanics - and seem particularly upset because now those intentionally bad design decisions [in terms of maximizing fun/challenge] are infecting console games.