We've been running delta live tables for some time with unity catalog and it's as slow as a sloth on a Hawaiian vacation.

Anyway, DLT had three consecutive failures (due to the data source being unreliable) and then the logs printed: "MaxRetryThreshold reached. Flow <my_flow> fallback to legacy execution mode. No user action required." After this, the pipelines ran like 3-4x faster. How can I force Delta Live Tables to use legacy execution mode?