How did you do? Is HTML already one of the languages you continuously keep up with?
This was definitely an (expected) humbling experience for me after 10 years of web development:
I feel like HTML can get glossed over in web development since it's not a programming language and therefore assumed you can just learn the tags at the beginning and never worry about it again. So many online courses have you "learn HTML in one day." Granted, you can definitely get started after a day but there is so much to continuously learn; I still sometimes struggle with selecting the proper tag to represent specific content for semantics and for accessibility. (Don't even get me started on form tags).
And based on this survey, there are so many new tags and APIs that continue to come out. There were so many things I hadn't even heard of. A lot may not be applicable to what you do day-to-day, but it's definitely a reminder to research things even if you think you already know.