I was much better back then compared to how I am now.
I was in a lot better shape/condition then than I am at the present.
「今よりはまだまし」は次のように言えると思います。
ーI was much better back then compared to how I am now.
「今の私の状態に比べると昔はもっとましだった。」
ーI was in a lot better shape/condition then than I am at the present.
「現在の私に比べるとあの頃はもっと良い状態だった。」
例:
I was in a lot better shape mentally at that time because I didn't have all the stress in my life that I have now.
「今のこのストレスがなかった分、あの頃は精神的にもっと良い状態だった。」
be in a lot better shape mentally で「精神的にもっと良い状態である」
ご参考まで!