When you apply any creme or serum, it clears excess melanin and controls melanocytes but nothing beyond that. So, you can expect a creme or serum to help you recover from tanning and restore your original skin complexion. But, if you wish them to make you whiter forever or fairer than what you were a child, that is not possible.
With this example, you might have understood that hair & skincare products need to be seen as lifestyle products and not a magical remedy.
So, stick to whatever suits you.
Try to take a break and see if your acne/pigmentation/dermatitis/dandruff/hair fall comes back if you stop using certain products? If not, maybe the concern was due to temporary hormonal changes, food habit, climate, pollution or stress. But if the problem comes back, consider using the product(s) as your lifelong companion.
That's why it's super important to choose natural & clean products only while trying to solve our hair/skin problems. Because if any product suits you and can solve your problem, you would want to marry it and not change it.