Changing your kids diaper out in the open in public around others is considered rude.
However you can change your kids diaper in public as long as you take the kid away from other people and then cover them up somehow to change their diaper.
Don't just change the kids diaper wherever you are if there's people around.
Such as for example if your at a table eating then don't put your kid on the table to change the diaper as that is gross and unsanitary.
Not everyone thinks it's cute to change your kids diaper in front of them.
Also give the kid some privacy and cover them up.
There have been times where my kids pooped their diaper and I waited until I got home or could at least get into our van away from people to change their diaper.
However if you're someplace such as at a park etc away from others then it's okay to lay the kid down on the ground and change their diaper but if there's people around you should cover the child up with a towel or something to give them some privacy.