The admin section of WordPress.com is in transition phase. There are two options to do admin work today. One is the old wp admin and another is new modern looking admin section. The wp admin has all the advance options. The modern admin section is slowly caching up. In the future may be the old wp admin section will be fully merged to new admin section.

Both the option was usable until now but in a recent update now you can choose which option you want to use.

https://wordpress.com/blog/2021/03/30/wordpress-com-design-update-for-a-more-intuitive-experience/