I wouldn't call it the same problem. Something nullable is similar to an Optional type (i.e. in scala Option[String] would map to a nullable varchar). That is not the same as being schemaless, you at least still have types that are being enforced, even if they might be empty.
I would agree that having too many nullable fields could indicate a problem with the schema, i.e. you should break things up into more tables.
I would agree that having too many nullable fields could indicate a problem with the schema, i.e. you should break things up into more tables.