I myself am half-Armenian, and while that is not a culture that has arranged marriage, it's got the common folklore of quasi-oriental clan civilisation. Parents are going to have a lot of input into just about anyone's marital choices, and it is understood on all sides that you're not marrying the spouse - you're joining families. So, there is a lot of opportunity for elders to object if a match patently doesn't make cultural (one might even say "civilisational" in extreme cases) sense.
That's what we don't have here. You're expected to dig out a partner from whatever corner of society you like, and if they suit you, great! There is something to be said for a paternalistic curation function, despite the annoyances and drawbacks of such a meddlesome way of living.
One of the drawbacks of a culture where, on the one hand, family input is very important, but on the other hand, arranged marriage as such is not a thing, is that it's all too easy for relatives to fall into the pattern of pushing the veto lever without proactively introducing you to someone themselves. If everyone's wrong for me, who's right? :) The fact that families have a matchmaking responsibility is an appealing virtue of arranged marriage culture.
There's a million variables to consider when having your own children, when you're adopting children you're adding many more. Sure, it could all work out wonderfully, but you're just increasing the random factor. See the recent movie "Lion" for examples of randomness, both good and bad.
What's wrong with having the same culture you mention, except for the fact that people can marry freely? You'd have the same benefits but hopefully with lower risk. If you want to work in the same cultural limits, just ask for advice (from your family, friends, etc.) before marrying and try to follow that advice.
Of course, the general problem is that you're asking 20s-something people in the throes of hot, passionate romantic love and attraction (in cultures which also celebrate romantic love!) to voluntarily submit to a plethora of mood-killing "cultural limits". Boo!
But it's probably still better than the American approach of, "look ma, no hands!" :-)
Westerners are always shocked that even educated people get arranged marriages in India. This is precisely why it works, all the groundwork is done for you. You are raised with similar memes, your arranged partner has been programmed into similar groves as you. Top that with a conformist culture where people try to fit than stand out, chances of finding something truly surprising about your partner are super rare. No amount of dating, living together can match this.
I used to find arranged marriages disgusting and backwards but now I have come full circle having looked at many of my close friends with successful marriages ( there is also aspect of higher social stigma of divorce, but thats another topic).