As long as you don't have them put down because you can't be arsed then I don't think getting rid of a pet is bad at all, its often in the animals best interest even.
Its not even terrible to get rid of a pet your not compatible with and get one you are. Living with anything is hard, pets can be like moving in with a boyfriend where even if you went in with love and hope you can't find out you just don't fit.
In my pre-teens I had a rabbit, it was given to me as a gift and it HATED me with a passion and as excited as I was at first I really grew to hate it too. It was the bloody devil in fluffy form, it was horny and angry. It destroyed everything, constantly attacked me, I had no idea how to cope and caring for it was impossible and wildly expensive.
I found someone who had given their child a hamster that she wasn't remotely interested in or looking after properly, the mother was trying to give it away but turned out the mam loved rabbits and had had several of the same breed in the past so we 'traded' pets.
I ended up with a wonderful hamster that I spoiled and doted on everyday until he died of very old age (for a hamster) and the rabbit went to someone knowledgeable, experienced and equipped to handle it. Over all everyone ended up happier and definitely the pets had a better life because of it.
I'm not a terrible person I just literally could not cope with an animal that despised me no matter what I did.
The above is also probably a warning lesson in not 'gifting' pets to people.