K18 did nothing for me - what does my hair need? How do hairdressers make it crazy smooth and shiny every time?

Prefacing this with autoimmune diagnoses I got a few years ago and they absolutely wrecked my hair. I used to be the girlie everyone was jealous of in school. Now my hair has lost about 50% of its density due to telogen effluvium bouts, and while I am prone to dry skin AND dry hair - I can get it under control with proper care. My skin has not only come back but actually become the best it's ever been. I narrowed skin care down to VitA aka retinoids, VitC, AHA/PHA and SPF. Occasionally VitB aka niacinamides, peptides, ceramides, and other actives (acelaic or tranexamic acid). I want the same for my hair. There must be something similar out there so it can be restored. These power actives and ingredients that are just *right* for my hair type and problems I have with it. Mostly snapped off ends.

I recently bought the k18 detox shampoo which my scalp L O V E S. It's the perfect formula. I feel clean but not dried out at all, and I personally find that it smells divine too. Very citrus-y.

I also bought their viral hair mask everyone and their mother has been raving about - and I got absolutely nothing so far. I expected that insane smoothness and shine Olaplex 1 gives me. But it didn't happen. What I can say after 2 uses of the k18 hair mask is that my hair feels maybe a bit fuller and stronger. But nothing crazy. I do use it exactly as advertised. After the detox shampoo on towel dried hair, emulsifying 2-3 pumps in my hands until the product turns an opaque white shade. Then working it into my lengths in sections and personally I don't condition after. I just leave my hair alone after the 4 minute mark the mask is supposed to take. So many videos reported that their hair instantly felt smoother even while putting the mask on and that hasn't happened for me either.

What am I missing? What does my hair need? Why is k18 not working? I was so excited to see what all the fuss is about and at that insane price I'm almost irritated it gave me absolutely nothing so far.

I am up to date on ALL labs and blood panels because my disease gives me deficiencies across the board. I made sure to erase them all with healthy lifestyle choices regarding diet&supplements, sleep, exercise, stress management. Very on top of it. My hair has improved too, but it's still this brittle, dry, straw-y mess. Thinning out towards the ends, which is my biggest issue. It used to be so full, luscious and shiny - now I can't wear it at waist length anymore because it just looks ugly. I want my smooth hair back 🥺😩 help a sis out pls. I don't wear tight styles and always let it air dry, so it's not mechanical or heat damage. I haven't used any color in idk how many years. It's virgin hair. It breaks because it's too weak and I'm at my wits end on how to prevent this from happening