Annuities: Worth or not?

So after research, I found that the Annuities concept, an alternative way of let's say a second retirement pension is not worth.
Although arguably it is designed for people who a) Can afford it b) Have zero tolerance with risk in an investment

I posted in some other forum and I got the reply that the only person who benefits from this investment is the actual agent who sold you this product. I asked why and I got few explanations but I had to cross-check with the best of the best, here in BHW.
So, your thoughts are welcome. Convince me that is not worth or differently. Anyone has experience with this?
Edit: To those not familiar with Annuities, it is like playing monthly an amount for the following 8 years minimum. After 8 years of payments they guarantee to you that you will have returns. Ideally you will have to pay for 15 years. Less than 8 years you have penalty. Hope that helps to understand the concept. Not sure the diagram is representative.