While I could discuss at length why F2P games are bad (as so many before me have done), I will instead focus on why the economics of F2P games force a reward schedule that is broken and parasitic.
F2P games are designed to appeal to the masses, but the development teams often only truly care about the 1% of their players who will pay their rent. They do need to create a space for players to play for free before they become hooked, which means there must be some level of needs satisfaction for all players. The mechanics in many F2P games work at your most basic impulses and needs, like timing rewards so that you regularly receive them (along with the associated dopamine) and so that you are always very close to the next reward. Many F2P games have very simple core gameplay loops that are very easy to get into and they make it very easy to keep playing beyond a few minutes. All gambling games do this because they want to attract as many players as possible to increase the odds of them spending money. By playing the core gameplay loop, the game will give you a taste of some bit of power, be that a magic jelly bean that makes the whole board clear in Candy Crush, or some other overpowered item that gives players a huge rush of dopamine. These are not earned like they would be in a better designed, non-parasitic game, they are purposely scheduled and gifted at the optimal time to keep you playing, now in search of the next hit.
The first one is always free, right? And in every game, you will find these power items are the number one item in the store for someone to buy for $0.99 (or buy the “Super Mega Deluxe For-kids-who-have-their-parents-credit-card Value Pack” for $99.99!). And it works! People love feeling that high, and the game is designed for them to pay money and get those regular doses. And if players want to ignore these, they can, but their whole experience will feel like the slowest treadmill toward the least satisfying ends, because the reward schedule is not the proper curve that a non-F2P game would have.