Other than our local McDonalds and the Arby's in the next town over, the drive-thru's I go to have you pull into a designated parking spot. At McDs you have to pull up to the next window if your order is going to be ready in less than 2 minutes. That window is more than a full car length in front of the main pick-up window. I've never had any issue getting around a car at that window. If the order is going to take more than 2 minutes or if there is already someone waiting at that window, they send you to a designated parking spot. And at Arby's, they have a sign that says "stop when driver's window is here" (which is also at the end of fence/handrail for the sidewalk so it's an obvious place to stop. That too is more than a car length away from the pick-up window. And if you have to pull up to that spot, the worker will emphasize that you need to pull up all the way to the end of the railing so that the the cars behind you can get around your car.
We did have that issue at our old McDs that they tore down 5 years ago to build the new one. Congestion in the drive-thru line was one of the top priorities to fix with the new building. At the old one (built before they ever had drive-thru's) there was barely enough space for one car to pull forward from the pick-up window. You literally had to pull up until your front tires hit the curb of the sidewalk leading out of the restaurant. That allowed enough space for the car at the pick-up window to be able to barely get around you. When you were in that spot and were ready to leave it could be a nightmare to get out. You sometimes had to wait until the next car coming up to the pick-up window noticed that you needed to back up in order to get out and they nicely would stop before they reached the window to give you the space to do that. Sometimes a worker would have to come out and stop the cars in the pick up line to let you back up. I always dreaded the "just pull up and we'll bring your order out to you." comment. When they built the new building it was turned 45 degrees which allows for plenty of space for the drive-thru traffic when you have to wait a few minutes for your order.