Usually the institutions will try to have the different kids with their parents at different timetables of the day and start on different days. Usually after a few days the parents will be sent out and gradually lower their time spent in the institution.
Also you normally have different professionals take care of different new kids so you don’t have to take care of all the parents and new kids every day.
Yes, it means you will have a few days and maybe weeks at the start of the kindergarten year where you got some parents there whatching your every move, but you get used to that very fast, especially if you have the feeling you know what you are doing (basically meaning experience).
Yes, it is a whole thing. There are different models with different time frames and it gets tought in the education of the daycare professionals.
I am talking kids aging 0,6 to 3. That is the lower range in Germany and normally you would start with daycare in that age frame. (Not taking into Account Bavaria. I think you get shot or something as a mother if you even think about giving your child to daycare there)
Usually it can be more difficult with older kids though if they have no experience in daycare, since they are more used to only relate to their parents and spending time with them. Also they might faster realize their parents are going to leave them there and that this is going to become the norm for their days. Understandably they are not gonna like that right off the bat.
I worked in other countries as well and it was quite a shock culture wise to have people expect you to rip the crying child of their arms and throw activities at them for up to 9 hours so they get distracted. As I said, sure, the child will cope over time and calm down. But in the long run I doubt it is a good thing development wise. Starting off you WILL distract them from their feelings and that is not the best way to learn how to deal with your emotions all the time.