I wouldn't see it in such black and white terms. straightening your hair daily isn't so much an absolute no-go and more a question of _how_, but also your hair quality. it's different for fine hair than for thick, strong hair. that's important to know before you follow any blanket rules.
but what often gets overlooked: temperature makes a huge difference. a lot of people set their straightener way too hot because they think you need that for effect. but you're doing way more damage to your hair at 180°C than at 140-160°C. if you basically need to straighten your curly hair daily to look normal, then do it daily with a lower setting and less jerky movements, rather than going through your hair once a week at full heat. plus: heat protection spray isn't just marketing - it actually makes a difference if you apply it _before_ straightening and not after.
your hair also gets damaged by other stuff (chlorine, sun, washing it wrong), so it's not like straightening is the one single thing you can blame for everything. if your hair is otherwise well-maintained and you control the temperature, straightening daily isn't automatically a death sentence.