i) Business pages that are easy to create and maintain for small, local business owners
ii) Facebook events for listing information and keeping in touch with registered attendees, as well as event discovery for users
iii) The importance for certain creators hosting their content and connecting with their user base on Instagram (assuming that would be also cancelled, as it is owned by Meta)
iv) Controversial due to the privacy implications, but a lot of companies rely on paying for Facebook advertisements to survive (which is driving why Meta is valued so highly on the stock market).
A tech-savvy user can create a website (or hire someone to); move to Eventbrite or equivalent; change photo-sharing apps to VSCO or equivalent; and back up their messages.
But many people don't know these are even options, or lack the funds and technical skills to do this (because their specialties are in non-tech fields, for small business owners and people in certain creative fields). The bottom line is that Meta and its constituent of Facebook are valued highly for important use cases that can't be easily dismissed.