Funny you should bring that up, because FB is a perfect example of a visual relic from the late '00s which didn't age well. Much of the post-dot-com-crash world of design in the web and early mobile space was defined by a rejection of the excessive - wild crazy idiotic irreverent and often incoherent - typography and design of the '90s web. So, super basic fonts, white backgrounds, and what they thought was "minimalism". However, because they relied on the tooling rather than creating their own cues, (and also because their UI turned into a towering nightmare of crap) Facebook looks extremely dated to most people's eyes now. It looks like a 20 year old website...and not a particularly good one.
My outside opinion is that Meta does not give a shit at all about how Facebook looks at this point. I'm not here to make the case that revolutionizing their design would improve their onboarding rate now or something. I'm making the case that if you are some nobody with no network effects and no billion dollars, you have a better chance at getting people to read your content if you take the time to (a) get it out of system-ui fonts and (b) make a bunch of other aesthetic decisions that trigger certain pleasing feelings in your audience.
My outside opinion is that Meta does not give a shit at all about how Facebook looks at this point. I'm not here to make the case that revolutionizing their design would improve their onboarding rate now or something. I'm making the case that if you are some nobody with no network effects and no billion dollars, you have a better chance at getting people to read your content if you take the time to (a) get it out of system-ui fonts and (b) make a bunch of other aesthetic decisions that trigger certain pleasing feelings in your audience.