I have a golden retriever in a 2 bedroom top floor (4 storeys) flat.
Ultimately, I think it depends on the dog but our dog is absoutely fine. He mostly sleeps during the day. He has two beds (one in the living room, one in the bedroom) and has lots of teddys and things he can play with. As we both work from home at the minute we interact and chat with him throughout the day.
He doesn't bark, pace, just chills out. He's pretty lazy but is very energetic outside.
In terms of walking, we go out at around 7.45 for 30 minutes or so. We then take him out between 12-2 for 30 minutes and then around 5.30 for 45 minutes to an hour. At 10pm we take him downstairs to a patch of grass outside for a final pee.
At weekends, we are out for a few hours each day. Today for example, we will walk approx 3 miles to take him to his friend (more below) and she'll walk him a fair bit. Tomorrow we will go for a walk around a loch so he can swim
Feeding? He gets fed twice a day, after the morning walk and before the evening walk. Feeding doesn't take long, literally a mug full of food into his bowl and a dentastick in the morning.
Before working from home, he got a dog walker each day my partner didn't work from home (she worked from home 2 or 3 days out of 5 pre Covid) then that's probably around £10ph or £15-20 for doggy day care.
We used BorrowMyDoggy in the past, and from that he's met a friend who he hangs out with quite a lot - in fact, she is taking him this afternoon so my partner and I can go for a cycle. She has also borrowed him when we go on shorter trips. For longer holidays, there's someone else we use who looks after him in her home and doesn't charge much. However, my mum has got a dog since our last holiday and is keen to take him next time so there's always that.
However, we do generally involve him with our day to day stuff. We know all the dog friendly pubs/cafes/restaurants in the city, happy to take him on walks. He's fine on the train so if we don't want to drive then that's that option. Again, for weekends away we just take him with us. During the break in the lockdown last year we went to Bristol. Drove down from Glasgow and stayed at the Hotel Du Vin which is dog friendly and is happy for the dog to be left in the room whilst we went out in the evening and happy for the dog to dine with us in the bar. Whilst we were in Bristol, we mainly walked around with him and had some drinks. One evening we went out to a fancy restaurant and he just stayed in the hotel. Once we got back I just took him for a pee. But, the majority of places were fine (I had to carry him up the stairs in Left Handed Giant as he was terrified of something for some reason!).
So you can definitely involve them in your holidays, it's just if you want to? We have stayed at a bunch of hotels/b&bs/holiday homes/etc with him. He's a family member to us so we don't have any issue making sure what we do can accommodate him.
Insurance - £30 or so a month, but that's with a bunch of claims (he has on-going hydrotherapy and on prescription pain killers)
Food - £35 a month.
Vet bills - £40 a year for vaccines/boosters.
I think it sounds like you don't want one. You have to accept that your life will change, a lot. And your weekends and free time to a large degree will have to involve the dog. If you don't want to sacrifice that, or can't involve the dog then it's probably not a great idea.
This is him now