Why can't I apply Vitamin C and retinol together?

Lately, I’ve been looking into cosmetic ingredients because I want to manage both skin elasticity and brightening at the same time. I found that Vitamin C and Retinol are the most famous ingredients, so I wanted to try using products containing both to create a synergistic effect. However, after searching the internet and beauty communities, I found many people saying that you absolutely should not apply these two together. It’s starting to scare me.

Both ingredients are so good for the skin, so why is it absolutely forbidden to apply them together? I heard somewhere that both can strongly irritate the skin, so using them at the same time could cause a complete skin reaction, which really scared me.

I want to brighten my skin tone and prevent fine lines, so it's hard to give up both. ㅠㅠ Are there really severe side effects if I use both products together in one routine?