Maybe that's why we have seldom sat down and exchanged our f

该句主句主语为that,is为系动词,why we...and thoughts为why引导的表语从句,充当is的表语.因此主句为主系表结构.
表语从句中,we 是主语,sat down 和 exchanged 为并列成分,共同与have构成表语从句的谓语部分,our feelings and thoughts为在表语从句中充当宾语.因此从句为主谓宾结构.
主从句没有语法错误,意思又讲得通,所以是正确的.