Why isn't it são apertados, like eu sou alto?
At the moment the shoes got tight, when the person tried them on. As we have no context, "os sapatos são apertados" should also be accepted.
Maybe they were tight just because they were new. Thanks.
Good conclusion ;)
I saw the same with skirt and "comprida"... is it because the skirt could be cut shorter?
Not exactly. This could mean the person is trying on the skirt at a store and the she hasn't been wearing this skirt for a long time. Then she got fat and realized it doesn't fit her anymore.