Another couple of aspects about the stoop or porch is that it needs to be large enough (and many architectural designs don't provide for this) for the people - one person or a group - to await entrance to the home by having someone on the inside open the door and welcome them. The entrance should be covered so that it prevents precipitation from making them uncomfortable as they wait - this is largely overlooked or under-addressed in home design also. Lastly, the entrance needs to be well lit to create a welcome feeling, a sense of arrival, and provide a feeling or security for those waiting to enter.
There are other considerations between the street and the entrance, but this notion greatly expands what commonly is thought of as visitability. If someone is hindered from gaining access to the home, it can't be considered visitable!