Flushing may not be good but changing the trans fluid is a necessity! The friction modifiers do break down on all ATF'* which then helps to wear/ build heat & then worse.
Plus the filter should be changed too!
bONUS- u also get to look inside the pan & find out how much particulate matter ie clutch plate /metal shaving etc are in there. Mine is clean as a whistle, but then I do trans service every 35k miles period.
Do your service & add to DEX VI (6)
LUBEGARD Automatic Transmission Fluid Protectant