We are using a direct query from Redshift as our Dataset to populate the reports. We have a table with 798M rows, and Dashboards are failing to load the data with a message “Getting Data for this visualization is taking too long. Retrying this request or importing this data into SPICE may help”.
Without further details on your workload, my answer might be a bit vague. However, it seems like the large dataset from Redshift is the issue. Some paths to resolution:
Optimize the Redshift Queries that you are making (aggregate data, limit rows, index, etc)
Utilize SPICE as suggested by the error message. SPICE can handle up to 1 billion rows and you can import your dataset into SPICE to reduce the query load from Redshift.
Other things to consider are to look at Redshift Query Logs for further investigation.