Really talented people don't talk about how good they are, other people talk about them instead. They are not all that special if they have to talk about themselves.
この場合、次のような言い方ができると思います。
ーReally talented people don't talk about how good they are, other people talk about them instead. They are not all that special if they have to talk about themselves.
「本当に才能のある人は、自分がどんなにすごいかを話さない。他人が彼らについて話すものだ。自分のことを話す必要がある人たちは、大した人じゃない」
They are not all that special. で「大した人じゃない」と表現できます。
ご参考まで！
大した人じゃない
- They're not much
- They're not all that great
- They aren't that special
- They aren't that amazing
『本当のtalented peopleは自ら自分を評価するのではなく、他人が評価するものだ。大した人間では無い』
- Really talented people will not evaluate themselves, others will. They aren't all that great.
- Real talented people will not brag/boast about themselves, others will. That person (he/she/they) isn't all that great.
カナダ 
アメリカ合衆国 
