As a child I was fostered many times due to having a mother with mental health issues (Munchaussen's by Proxy and Psychopathy).I never once blamed the foster families for taking me away from my mum Connemmara,I don't know where you have gotten the idea that most foster children feel that way.
There are different types of foster parent,you can be an emergency foster carer or long term.Emergency is very disruptive to family life,you can be woken in the middle of the night by social workers trying to find a placement for a child at risk etc.
Expect to have every aspect of your lifestyle probed intensively.You must not be a smoker,have strong political or religious views and of course be ready to accept a child of any nationality the social services think would be suitably placed with you.You can refuse to take particular children if you feel strongly that it would be too much for your family to cope with.
Good luck with it all hammerman.