Display table is good and I use it most of the time but it is no good when you want items to wrap to another line and fill the next line automatically. You have to manage tables in rows and once you define the rows you can’t then have two or three in a row.
When you use flexbox you can most of the time apply display:inline-block to the flex child element as a fall back and still have it look reasonably good in ie9 (inline-block has no effect on a flex item in browsers that support flex).
Flexbox browser support is now at 95% so its time to start using it when needed (not for everything though).