I didnt see almost anything hard about Three Body Problems. I only read first book, because the story was not that interesting.

I dont really read sci-fi that much, but Blindsight has been ten times better when it comes to hard scifi

Well I suppose that’s personal taste. Book and the series is categorised as hard fiction on the basis of gravitational physics problem woven into the plot and taken much further into next two books. Your definition may not align with it but it’s very odd to compare two different work based on personal taste rather than merit.