I built a web framework in 2005 based on table layouts. Years later I switched to Flex (when it was available, and when Grid was still poorly supported.) Some years ago I switched to Grid because it was more generally supported.

So I expect that what you are mostly seeing is the evolution of CSS, from table to flexbox to grid. Table has no real responsiveness (to screen size), Flex does it _really_ well (especially for cases where the target is both PC and Phone etc.) But it has some limitations (mostly for me around column widths and the concept of "relative" column widths.)

Grid is really nice, it's a lot more like tables in concept, but at the same time has responsive abilities. These days I'm grid-first, although there are still a few places (depending on context) where flex is more appropriate.

Of course flex is also more "well known" (because it's older.) I feel a lot more comfortable there still, and until we have sub-grids I'm also a fan of using Grid layout for the "outside" and using Flex inside specific cells.