Creationism seems no common core beliefs beyond that some deity created something. For example Christian Creationism has two source tales found in the Bible, tales that are contradictory in the order of creation, method of creation, descriptions of the creator and then whole host of extra Biblical fantasies.
Then there are the equally valid creation myths of the dozens or hundreds of other non-Christian religions.
Since there is zero evidential support for any of the many flavors of Creationism they are at best belief or mythological systems.
Re: Creationism whatever some group wants it to be.
Of course I would classify them as Creationists.
And all the other Hindu or Buddhist or animist creation myths as well.
The reason Creationism is so worthless as an explanation is that it is whatever fantasies a peoples create. Even in the Bible there are two mutually exclusive creation myths that differ in the order of creation, the method of creation, even in the description and characteristics of the god doing the creation.
When you add in the fact that there is no evidence of any special creation and almost all the various creation myths are refuted by the evidence found in reality the only possible answer to the question "What is creationism?" is "It's whatever some person or people what it to be!"