Sure, but an individual website may use only a few of those standards. Ladybird devs will pick a website they like to use - Reddit, Twitter, Twinings tea, etc. and improve adherence to X or Y standards to make that one website look better. In turn, thousands of websites suddenly work perfectly, and many others work better than before.
Ladybird is largely conformant to the majority of HTML standards now. It’s about the edge cases (and where standards aren’t followed by websites) and performance. This isn’t a new project.
It would be nice if people read the post and the project before randomly making assumptions such as implying the project started from scratch yesterday or its run by some amateurs, this is a 4 year old project! It’s founded by a former KHTML/Webkit developer for Apple!