old hat 
noun [mass noun] informal
Something tediously familiar or outdated: last year’s electronics are already old hat...
- So, you know what is - what is sort of banal and old hat to one group of people, is brand new to another group of people.
- I know it is old fashioned, and old hat, but Terry loves a good yarn.
- Suddenly native plants were thought dull, common and old hat; gardeners began to reject them, banishing them as weeds.
Synonyms
out of date, outdated, dated, old-fashioned, out, out of fashion, outmoded, unfashionable, last year's, frumpish, frumpy, out of style, outworn, old, old-time, old-world, behind the times, archaic, obsolescent, obsolete, ancient, antiquated, superannuated, defunct;
medieval, prehistoric, antediluvian, old-fogeyish, old-fangled, conservative, backward-looking, quaint, anachronistic, crusted, feudal, fusty, moth-eaten, olde worlde;
French passé, démodé, vieux jeu
informal square, not with it, out of the ark, creaky, clunky, mouldy
North American informal horse-and-buggy, rinky-dink, mossy
archaic square-toed