Although not all F2P mmo's have horrible cash shops with insane prices or pay2win items the problem lies in the fact that I'm a bit prone to addiction.
Nowadays there are not only you buy what u see items in the shop but also boxes / cases which u need keys for to open them.
The keys can drop in game but most likely will not and to see whats inside you have to buy the keys
from the shop. In this way its more like a lottery and its a pure gamble if anything good will come from the boxes.

When you are a bit prone to addiction you keep wanting to buy keys to open boxes because of "what might be in the next one"
IRL its pretty easy to stay away from things like that but when they start putting stuff like this in the games u want to play it can be a bit of a problem.
F2P seemed like the holy grail at first, you don't pay for a sub, you don't feel forced to play the game because you are paying for it, you download and play, don't like it? no problem just uninstall, its not like u payed for it.
but because of these shops and the amount of money i spend in them id rather go back to the subscription model, because in the end its way more cheaper for me then F2P.