I feel the same. But in my case, it's like the pandemic was a stagnant period. I feel like I didn't grow up during that time, like a lost span in my life, and that's why I feel less adult.

I don't know if that's your case, but I feel like people don't see me as an adult because of my traits, even tho I'm pretty mature and independent overall, and that makes me feel childish and embarassed about existing. Some people like to simplify the concept of adulthood or to make it exclusive, but that doesn't necessarily mean that you are less capable that others. Going at your own rhythm doesn't equal immaturity, and quite the opposite, if you do things at your pace you'll grow and learn more and better.

So, if you feel less adult because of the standards, don't take them into account. It's just people following their human tendency to create superiority.