I wouldn't say that 'sense of individualism' is a uniquely modern thing, or it goes to any extreme as 'individuals over community'. In fact nowadays, especially with the emergence of Internet, we appear to be more aware of how we, as individuals, can impact community. The difference between us and the 'old world' is that we do so on more of a global scale, rather than just within our smaller communities.
Solas is also not one who'd I'd describe as holding a traditionalist, collectivist mindset - even his quarrel with IB shows just how much he values individuality.
As for Solas not understanding Varric I don't think this is about being 'okay to be a surfacer' - what he doesn't understand, either in surfacers or Orzammar, is why neither of them dig up their own history, which could probably help them grow, or understand better either themselves or the world around them. He doesn't just ask Varric about being happy here (in fact he commends him for making his own path and being appreciative of what he has), but cannot understand why they're not interested with their missing connection to the Stone OR why Orzammar isn't doing anything with lyrium, other than trading it and adhering to tradition.
He makes it seem as of the truth about the Titans is within the reach (just like he says that anyone who can dream has capability to interact with spirits, but few ever try) and what he's baffled by is people's willful ignorance or lack of curiosity. THAT, I think, is one of his major gripes with the world - lack of inquiry, skepticism or cultivating critical thinking skill. Ironically, it's a very "modern" mindset, at least on meta level.
I was thinking more along the lines of people like Sera or Varric, who for them, their identity is about who they are as a person, and less based on what they think a dwarf or an elf is supposed to be according to their ancestors, etc. They don't put a sense of duty to Dwarven or Elven people first, but to the people they care about and who share their values, who may or may not be Dwarves or Elves. That sort of individualism to make and define their own groups, or way of life.
Solas might share that individualist attitude, but he's obviously struggling with his sense of duty and obligation to his people now, regretting what he did in the past, and the world it has resulted in.
He does compliment Varric's ability to leave it behind and make a new future, but suggests he doesn't have the ability to do the same. So yeah, I do think there is a theme here about the clash between old and new world. How much do we keep and how much do we let go of, etc.