Paid mods have been a thing for Bethesda games for a long while; that's effectively what the Creation Club is.
In any case, they haven't introduced paid Starfield mods yet (nor have they introduced official support for Starfield mods at all), so until that happens it ain't (yet) a live service game.
But, I'm not sure it's accurate to say it isn't a live service game, as it's been clear they've wanted to introduce paid mods.