You can definitely have a dobe or really any dog with a 9-5 job. I work 7-430 every day and my dobie do just fine. That said it does take extra effort to make it work. I don't want to undersell the amount of time and effort it takes. It's a lot to make it work. I get up at 530 every day to take him for a nice walk before I leave for work. I try to come home for lunch most days to break the day up a bit. As soon as I get home it's time for training and exercise for at least the next hour. The rest of the night he spends pinned to my side and we often end up wrestling around and playing tug throughout the even as well. I let him sleep in the bed with me too. I also take him with me everywhere I go unless I'm going somewhere that I can't bring him. So it's doable. Does it mean your life outside of work is going to revolve around your dog? Probably.
The key is being honest with yourself about whether you can get up that early every single day, and be that consistent and put the time and energy in even if you are exhausted and had a bad day at work. It's not easy but I can't imagine NOT having a Doberman so it's worth it to me. I love my boy and we do literally everything together, watch tv, exercise, go out for a car ride, and of course all the typical doggy activities like fetch, obedience training, tug.. etc etc. We people think of me they think of me and my Doberman.
It takes a level of self awareness though. Can you put in that effort? Can you make the sacrifices necessary to make it work? If you honestly can then go for it. If you aren't 100% certain then don't because it's not fair to you and it's not fair to the dog. But, you can absolutely have even a Doberman with a 9-5 job and I hate this common advice today that anyone with any sort of life outside their own home can't own a dog. If that were the case then most people couldn't have any dog let alone a Doberman. It's not about dog or no dog, it's not about job or no job. It's about you, the owner and what you are willing to do and just how much you really love and want that dog.