Characters based off yourself get a bad reputation from those who just go overboard with a self insert, and just throw them into whatever canon and do whatever, as someone (sorry im tired and forgot to check names) already mentioned
plus if every character you make is completely based on you, then you dont get a lot of diversity in what you can do, as you limit yourself to your own experiance. Its nice to broaden your horizions if you make lots and lots of characters.
But theres nothing inherently wrong with giving a character certain traits of your own. One of my favorite characters i’ve made, Katari, started completely as a projection of my bad traits and such, and slowly developed from there. A lot of my characters have some aspects of me, which makes me able to relate to some of their experiances, but i still make sure they are their own person with likes and intrests that perhaps dont align with my own. Its just keeping that balance, especially if you’re not good at playing characters that are super diffrent from yourself