昔の人が考えられなかったくらい、技術はここ数十年でめっちゃ進歩してる、ってなんて言えば自然になりますか？
I think technology is incredibly progressing for a few decades as people never would have imagined.
かなと思ったのですが、細かい所がわかりません。宜しくお願いします！
I think technology has progressed in ways that people could never have imagined.
People a long time ago would have never thought technology would have advanced the way it has over the last several decades.
ーI think technology has progressed in ways that people could never have imagined.
「昔の人々が想像もしなかったように技術が進歩していると思う。」
昔のある時点から比べて技術が進歩したことを言っているので、現在完了形 has progressed を使って言えます。
people could never have imagined「人々は想像することができなかった」
ーPeople a long time ago would have never thought technology would have advanced the way it has over the last several decades.
「昔の人々は技術がここ数十年のように進歩するとは思ってもいなかっただろう。」
over the last several decades で「ここ数十年で・過去数十年の間に」
People a long time ago would have never thought で「昔の人々が思いもしなかった」
ご参考まで！
カナダ 
