저렇게 사람들이 다 알도록 입양을 하는 걸 보면 세상이 참 많이 변하기는 했어.
=> Judging from the way they adopt a child like that not minding other people knowing, the world has changed a lot indeed.
(Korean society used to be uptight about matters of blood lineage, so people looked upon adoption as something less than commendable. The sentence is observing how things have changed so much that no one seems to have this negative attitude on adoption anymore.)
* VERB-는 걸 보면 = (lit) if you see (someone) VERB => judging from how they VERB.
* VERB-기는 하다 = It indeed VERB. (It acknowledges something, with some vague implication like a reservation).
변했어 (it changed) is a simple statement, while 변하기는 했어 is nuanced, like "it has indeed changed (but it's still hard to believe it / but I haven't fully realized it before / but I don't like it, etc.). The phrase can also repeat the same verb instead of 하다, as in 변하기는 변했어.
1. A: 밥 먹었어. B: 응, 먹었어. "Did you eat? Yes, I did - simple with no nuance."
2. A: 밥 먹었어. B: 응, 먹긴 먹었어/했어. Nuanced, like "I did, (but it wasn't really a full meal)".