Hi John! I haven't exactly used Airbyte yet, but I've definitely read the docs and followed it's development for a little while.
I would say that Airbyte more closely solves the use case that Fivetran appeals to - consolidating internal company data and doing some light transformations before using the data for some analysis/reporting.
This use case is more for developers that are working on building out integrations for *their* customers - as I understand Airbyte, it wouldn't exactly fit this use case.
Let me know if I'm mistaken though, I'd love to explore Airbyte further!