Editorial work is as important as the technical “peer review”. A scientific paper needs to be not only techcnically right but also be readable.
When I have peer reviewed I focus in the technical aspects but I also add my personal engineering point of view. As an example, if I see something that is technically correct and ingenious, but I fail to see how it could be implemented in practice or economically, I ask the author to add a comment on his perspective of how this aspect could be boarded.
One annoyance is that many Peer Reviewers tend only to pay attention to "their slant" on what is done - where your work intersects theirs - and this may be partial or not very relevant. But that can easily be dealt with - it does little harm - and you also get reviews which are not so focussed and give very useful overall "here is what I think from the outside" help on how to make the arguments stronger or clearer.