The transition of the major social networks over the last 10-15 years -- from being a space for friends to interact to being a space to consume content produced by "unconnected" entities like influencers -- has created a huge opening for someone to claim the friends and family network. There is no one better positioned (at least in the U.S. where iPhones are the majority handset) than Apple.
So long as Facebook remains available to everyone, even if the content feed is a mess, the event planning space is going to be more accessible to everyone and will end up being the defacto friends & family ecosystem.
I'm not an iCloud+ member, so I can't go in an look for myself, but ideally this would be just a fancy way of extending your iCloud Calendar invites where Gmail, Outlook, etc. users can still create events and invite people in roughly the same way. If as a Linux & Android user I am only able to RSVP to Apple users' invites, but I am never able to invite them to anything myself, then I literally cannot embrace this product without investing considerable money into their hardware, which I am not going to do.
Hell, if they featureset was compelling enough, and they had an iCloud app for non-Apple hardware platforms, I might actually consider being an iCloud+ member, but I guess it's not worth it to Apple to collect a monthly payment from me if I won't make the downpayment on an iPhone and a Macbook...
For now. We're in the process of seeing Twitter die like every other social network has died before it, Facebook will have it's time as well.