It's really not complicated at all.
You really have three options:
(1) Move the data into a SQL-based database, and then connect Tableau or any BI tool to that database. There are data services (typically called "ETL") that will do this for you. A good example is Stitch Data (example:
https://www.stitchdata.com/integrations/quick-base/) depending on your volume that could even be free. I'd recommend if you're not looking to spend a bunch of money, to either use Google Cloud's bigquery or Heroku's postgres as your database.
(2) Use an ODBC driver for Quickbase (example:
https://www.qunect.com/) - Open Database Connectivity (ODBC) is a tool that can run on your machine or server and lets Quickbase "pretend" to be a database - and then just connect Tableau or other BI tool to that ODBC/translator-created database.
(3) Use Tableau's Web Data Connector (WDC) framework to connect directly the Quickbase API - this approach is pretty similar to using an ODBC, but its just using less software and is specific to Tableau (example:
https://www.quicktab.xyz/">https://www.quicktab.xyz/">https://www.quicktab.xyz/)
Happy to follow up with pros/cons of each if you're still interested.