Why is NiceHash not profitable?

Could you elaborate on why some people believe that NiceHash is not profitable? Are there specific reasons behind this notion, such as high transaction fees, low mining rewards, or competition from other mining platforms? How does NiceHash's profitability compare to other similar platforms in the market? Additionally, what strategies can miners implement to improve their profitability when using NiceHash? Understanding these factors may help us gain a clearer picture of why some perceive NiceHash as unprofitable and what can be done to address these concerns.