You should really reconsider. You had a bad route or bad first day. In the 30 routes or so that I've done, only 3 have lasted 4 hours or more. That includes the second I pull up to check in to the very last package. The majority lasts roughly 2.5 to 3 hours.
My first week recap was posted here: https://uberpeople.net/threads/my-amazon-flex-experience.77697/
My longest day was when I had 22 packages. Took about 4hrs and 20 mins and ended up in 4 towns. The most packages ever was actually today: 67 packages and took 3 hours and 3 mins (from check-in to returning to warehouse for undeliverable package).
Get the packages in the car quickly and get out of there. No clue how people spend 40+ minutes loading their car. Typically, start on the bottom right of the cart and work backwards and up. The top left of the cart is usually the first drop offs. Each route will have 5-8 chunks. Look at the numbers in top right of label, 0895, 0900, 0905, 0910, 0920, etc. The lowest will be the first set of deliveries and so on. All of the packages with these numbers will be delivered before the next chunk.
And for God's sake, stop knocking/ringing door bells. Simply select "left at front door". Of all the packages I've delivered, only 2 actually required signatures. Just leave them at the door, like every other package you've ever received.