I saw this pointed out in an episode reaction thread, but I'm pretty sure "Tomorrow and Tomorrow and Tomorrow" marks the first time the Federation has been explicitly, on-screen referred to as "socialist". Fans, of course, have been calling the Federation socialist/communist for a long time. I think it started kind of crystalizing in 90's Trek, particularly on DS9 and with Picard's little speech about not using money in First Contact.
It's kind of a throwaway moment in the episode, but it feels big to actually use the word? I suppose modern audiences are much more comfortable with the word than they would have been in the 90's.
To be fair, she's apparently been around more or less for the entire length of human civilization. She's lived under lots of different economic systems, and from her point of view the Federation was basically founded yesterday. Skepticism makes sense in that context, even if she generally approves. We the audience know that by the time of TNG, DS9, and Lower Decks (I have not watched enough Discovery to know if the far-future Federation is still portrayed this way), the Federation has if anything only gotten more post-capitalist, so I don't know that we're meant to read her skepticism as wise. I mostly took it as her being defensive and a bit flippant.