More seriously, what you describe is quite doable with flexbox (flex-direction: row, flex-wrap: wrap and flex-grow: 1).
Interestingly, even the Masonry layout was already doable using a simple multi-column layout, the "only" issue is that instead of having the items left-to-right, top-to-bottom (ordered by row) you have them top-to-bottom, left-to-right (ordered by column) which is not what you want most of the times
There's a CMS I use that has a photo search option. It loads in images in a column ordered masonry layout, which when you scroll down adds new images to the columns, so all the pictures move about and you've no idea where you are.
More seriously, what you describe is quite doable with flexbox (flex-direction: row, flex-wrap: wrap and flex-grow: 1).
Interestingly, even the Masonry layout was already doable using a simple multi-column layout, the "only" issue is that instead of having the items left-to-right, top-to-bottom (ordered by row) you have them top-to-bottom, left-to-right (ordered by column) which is not what you want most of the times