Maybe you can form one of your own? It's not as formal as a yearbook, but if you get a scrapbook or something (or maybe even something digital) and put all of your photos of your friends and school achievements/moments, you could make something like it!
And also, include a few pages for people to sign :P
Tbh, all a yearbook is a big expensive book full of photos and a place to put signatures. The only reason I got one is because one, it's my final year, and two so I could immortalize people and their signatures. Not everyone at my school was able to get a yearbook and had other creative names of getting people to sign.
And social media also exists so it's also a way to place your memories, keep them forever, and share them with others (as long as nothing happens to the account but also just upload your important stuff to the Cloud as well)