“Moses Mendelson was Orthodox?”
Mendelssohn’s contemporaries Rabbi Yaakov Emden and Rabbi Akiva Eiger took him seriously as an Orthodox scholar (and argued on his conclusions). After his death people used his name to justify things he would never have endorsed. And he would have been absolutely horrified at the actions of his children after his death.
” Shaul Lieberman?”
His contemporary Rav Hutner tried to recruit him to Chaim Berlin. Another contemporary Rav Soloveitchik was willing to serve on a Beit Din with him, and praised his Tosefta commentary. (Yesterday was his 30th Yahretzeit.)
” Avraham Burg?”
He was Orthodox but he may no longer be.