I always take esuna because it is my job as healer to heal their debuff too (if it can be remove)

Esuna is definitely a must for me, i dont like seeing a red icon on my party the same as seeing my party hp going below 50%, i play healer because i want to help and support my party, not "i play healer because fast queue time and when something going wrong i blame someone else and 120% not my fault"

I saw healer who didnt remove poison or other removable debuff because they didnt "feel" need to do so and when i ask why, their answer is either "their fault, they can just avoid it" or "eh no worries its only last xx seconds"

Yes they could avoid it but that mean they can bork their rotation and dps, some dps dont like it and as former dps i know that feel (ugh paralyze). all healer need is press a button and 1 sec later bye bye debuff, its sound not important at all but trust me, dps will love you for that.