MIndMaybe you should stop playing on a toaster. This is like saying "they're forcing me to play soccer on grass when my shoes have flat surfaces and have shit grip on it and great grip on concrete, literally unplayable on grass, WTF"
the problem is that not everyone can afford good pc, you can't just say "Maybe you should stop playing on a toaster.", some people spend all money on studies and/or on food, flat and clothes or are 10-15 yrs old and parrents aren't willing to buy them new pc.
and now my actual thoughts (like somebody cares): it'll hurt many people but it allows some stuff to be inplemented (outlines, more skins( = more money for valve = more money for tf2)) and nobody forces you to play mm whitch (hopefully) will be only gamemode/place you will forced to play with dx9, if they just remove option to switch to dx8 then they'll make many people angry, so hopefuly they won't do it. but generaly it's just bad, because with dx8 game feels different (better for someone) and people who spent 12k hrs playing on dx8 switching will be (hard maybe) annoying and uncornfotable and bad feeling customer is not a good thing
but i'm sure that somebody in this community will find way (if needed) how to launch tf2 in dx8 (there is a way how to play tf2 in dx7, dont know if it still works ) and (hopefully) ETF2L, ESEA and UGC wont force you to play on dx9 using server settings, you might be forced to on lans/events sponzored by valve tho