Highlift tints generally use 12% peroxide solution which is far harsher than using bleach with 6%. They’re good in some circumstances but if your natural hair colour is light brown or darker and you want to be a light blonde, your hair is always better off using bleach with a low strength developer and taking it slowly.
In my experience, the clients who say they’ve had a bad experience with bleach is usually due to user error, either a home diy-er who doesn't really understand what they’re doing or a poorly trained hairdresser.
They might use a solution that’s far too strong thinking it will speed up the process and/or overlap the product onto already fragile hair, especially if they’re trying to remove old colour. Olaplex can’t cure poor decisions.
It happened to me back in the 80’s, long before I trained.
A hairdesser used a very strong bleach solution to lift my light brown hair and it was so bad, lots of it broke off near the scalp. I had to have a very short pixie cut for ages afterwards as my fine hair grows quite slowly and I never let anyone else colour my hair afterwards.
If you‘ve been using Highlift tints (with 12%) on your hair for a while and if your hair has any length to it, you need to be very cautious trying to highlight already potentially fragile damaged hair. If you use styling products that contain silicones, they mask the damage to an extent because clients wrongly assume that the softness is healthy hair but viewing it under a microscope will tell you a different story.
Take a strand of hair and wet it then stretch it and let go. Does it stretch and spring back easily? Healthy hair will stretch and recover easily, damaged hair has less elasticity in it.