I understand that if you've had trouble with slots as you describe, that it's not the most pleasant. But our review is not made up of such things. In such cases I would ask the support what is the problem that your slots are not loading. Maybe you will find out that the game provider has some problem or there are some restrictions. Anyway, I can see that you have done so, which is wise.
Unfortunately, if they have given you that information, then that's the way it's probably going to be and there's nothing you can do about it. The providers themselves determine who can play their slots.
From what I've read, I have a feeling that this is the only problem. But of course it's your opinion and as long as you expressed it politely, I have no problem with it at all.
Regarding the slots and the fact that they are limited, what are some examples that claim to be available but probably aren't ?