Stitch is not good at replicating document stores like MongoDB to relational databases. To be fair, this is a difficult task. Stitch flattens the objects, but the result is unwieldy.
Stitch cannot replicate the same source to multiple sinks, which is inconvenient if you want to replicate some of a datastore's tables to Redshift and others to Redshift Spectrum, for instance.
Stitch, or Stitch Data, now from Talend (acquired in late 2018) is an ETL tool for developers; the company was spun off from RJMetrics after that company's acquisition by Magento. Talend describes Stitch as a cloud-first, open source platform for rapidly moving data. It is available on a Free plan, and also a Standard and Enterprise plan which include more advanced features (e.g. an account manager, multiple data destinations, HIPAA compliance, advanced scheduling).