I think the Facebook CAPI Beta has been in place long enough now to take it to the next level - allow more than just page view events to be synced.
Facebook's CAPI Gateway solution and manual implementation options are expensive for small businesses to implement and operate.
The CAPI by Hubspot is so limited right now because it isn't a full CAPI solution, especially for B2C businesses. Apparently it's limited to essentially lead capture and page views, rather than lower funnel events, and we're seeing that ourselves.
If someone knows differently, let me know - but it feels like the minimum Hubspot should be able to offer to Marketing Enterprise customers is a proper CAPI now, after over a year of Beta testing.