I have very recently lost my beloved dog after more than 14 years. I don't regret having him at all, but I don't think we will be getting another.
There is no denying that it's hard work, especially for the first two years if you get your dog as a pup. I haven't any experience of taking on an older dog - that may be easier, or more likely, the difficult period may be shorter.
If you are lucky, as we were, to get a healthy dog, once he has settled into adulthood there is what I would call a long 'golden period' where you and your dog have adjusted to one another, your dog is trained and well-behaved and he is simply and wonderfully a member of your family.
Finally, things may be more difficult again when he is old and his health starts to fail - toileting accidents, visits to the vet - and then the ultimate trauma of his death.
But however well your dog behaves there is no denying that they put restrictions on your life. Trips to non-dog friendly places (e.g. most zoos and theme parks, and most indoor attractions) either require a dog-sitter or to be kept very short; similar for events such as weddings. A dog becomes another worry during difficult family events such as illness or bereavement as his needs must still be met.
Taking your dog on holiday is a joy, but as they can't normally be left alone in your accommodation, you must be out in all weathers or in your holiday accommodation - no taking advantage of the rain to visit a museum or stately home unless you can find a dog-friendly one. There are odd things, like where we took our dog on holiday there was a swimming pool you could book, but my husband and I could never use it because it didn't allow lone swimmers and it didn't allow dogs.
Finally there is no getting over how generally messy dogs are - they bring in dirt, they shed, some toileting accidents are inevitable in the lifetime of a dog. You have to find your own compromise between lowering your standards and upping your cleaning.
We miss our little chap dreadfully and without him we feel lost; at every point in his routine, letting him in and out, walking him, feeding him, we are reminded of our loss. But we are older now and entering a phase of our lives where, over the lifetime of a dog, we are likely to have to face changes, so we have decided that it would be kinder to ourselves in the long run not to take on another.