Just because they may be advanced or have some other unworldly
perspective beyond ours, how do you know they want to make our
lives better?

Christian missionaries wanted to "improve" the lives of the natives they
found and essentially trashed their cultures in the process. I know this
is fictional, but the Borg in Star Trek see their assimilation of other
species as a way to "improve the quality of [their] life", to quote Locutus.

Even God, who constantly said he loves us, also kicked plenty of butt
and worse whenever humans didn't do exactly as he said, and God is
supposed to be omnipotent and all-knowing. So assuming every other
being in the Cosmos is less than perfect, what are they up to?

Unless you know something about the motives of such beings that I
don't (and I know you will tell me if you do), is it wise to just open up
to an alien species and assume they are looking out for our best interests?