Yes, it is. No Republic of Pirates or Edward Teach was promised when you purchased the game. This is additional free content.
I just pointed out the notion of "free" content as not being free because I think statements like "well I´m not sure I like Pirates but since its free its ok" misses the point of weather the pirates are a good addition or not.
Why is it not free?
Lets consider another situation. Lets say they almost finished the game and is about to release it (for say 100 $). But they push it out a little bit to early and not including content originally planned for the game (lets pretend Great Britain as a civ was cut to rush the game) and still charge 100 $ for it. When they then at a later time release Great Britain as a "free" DLC, is Great Britain then "free". You could argue, it was not in the base game and so the content is free.
Havent this happened with civ 7 by the way? Havent peopled done data mining finding perhaps cut content from the game (including the pirates)?
But I´m not going to continue arguring about what is free and not, since that is not what the thread is about, but as the saying goes there is no such thing as a free lunch...
Anyway, weather you regard the pirates as "free" or not is irrelevant. The point is, Firaxis have used resources (weather you regard the resources as something provided by the consumers or given "freely" by the company to create the pirate civiliztion. If we rephrase the question as:
Do you think those resources where well used creating the pirate civilization or would you rather have seen them adding some different content? Be that a different civilization or adding/improving game mechanics,
I for one really dislike the addition of pirates as a civilization:
Firtsly: It is not a civilization in the same vein as the other civilizations in the game. They are more to be regarded as a offspring or some aspect/facett of human civilization. If they can add loosely tied criminal organizations as a "civilization" then there is no limit to what can be added as a "civilization"/leaders. East india company? Tech conglomerates? Banking consortiums? The Hanseatic league? Mercenary companys?
I think that if they wanted pirates as a "playable faction" they should have added it as a mechanic to a civilization who have been known to harboring alot of pirates. And maybe added Edward Teach as a great admiral for those who want him in the game.
Secondly: The resources could have been used better. Including other classical civilizations and or leaders. Or perhaps adding QoL features.
Anyway that was my two (or perhaps three) cents about the addition of pirates as a civilization.