I really like the general look and feel of masonry/waterfall layout, maybe it's because I grew up reading physical newspapers (and still do), but to me a columnar layout is just an intuitive way to divide up a page.
I just wish there was an alternative to the default masonry ordering, which afaik is a simple rule that goes sth like 'place the next item in whichever column it can go up highest'. This means that the left-to-right order is really juggled from the second row onwards. What I imagine would be really nice is if there was a layout that preserves more of the left-to-right (or right-to-left, if that's your preferred direction) reading flow. Something like 'put the next item one column to the right of the previous item (or in the leftmost, if you were at the rightmost), unless you can put a second item in the same column without the new bottom going too far below the bottom border of the column to its left'. This would be more flexible than strictly going left-to-right (which would also mess up alignment) and would reatin some meaning of the left-to-right reading direction.
I know it won't be possible to accommodate every possible formula one could prefer for masonry, but if you have content where the ordering matters at least a bit (maybe not for Pinterest, but for a journal eg it would), then I really think sth like this would be a more sensible default than the classic masonry rule.