One time we get older, our priorities change.
A fall before we are considered old is just a fall.
An older person falling can cause end of life issues.
A neighbor fell last Friday, when help came said she was ok, next day her son checked on her, she was very sick, he took her to the ER and she was dead that evening, they think from a blood clot caused by the fall, the kind of blood cloth younger bodies rarely experience.
My point of this sad story, I too always preferred bigger dogs without a second thought, although had some little ones too.
My last dog was on purpose a little one, just naturally easier to handle for someone reaching old age, your main problem don’t trip on them, they are not going to bump on you in an exuberant moment.
I think that boxers are large very vigorous dogs with careless body awareness, not exactly the best for someone reaching natural old body limits.
That would be my main concern, admitting that if you like a dog, you will deal with size just fine.
Just one more point to be aware of here.
Even having a busy ranch life, many hours outside working, my life was no match for one of my border collies over the top, neurotic energy needs.
She would have loved 24/7 work to do, was unhappy every moment work ended until something else came up, nothing mattered to her in life but work, which she was great at, not happy just going for walks.
She would run along a dirt road and chase and try to head the dust balls the wind made of her tracks, for hours on end if you let her.
My standard worth repeating advice when acquiring a dog, always think of the dog too.
Don’t let it keep you from a dog you really like, you will make whatever work, but if you have a choice, weigh all a dog brings to you AND what you do bring to the dog.
The better the match in temperament and energy level, how much exercise and entertainment any one dog will require, for the given circumstances, the happier everyone will be.