I run a professional services org that helps you switch to an open source alternative. We'll host the solution for you if you want and aim to be drop-in Fivetran compatible in your workflows with a transition plan so you can run the thing if you'd like. Pricing is flexible. Personal email in profile.

Can you say more? Is it the unpredictability, or just too expensive?

They charge based on the highest number of unique rows transferred for the month. It gets expensive quickly.