I worked for Tableau before the acquisition and left a year or two after. It was pretty clear to insiders that there was never a good path to a smooth integration of Tableau into the SF platform. The teams have wasted years on that and are still struggling.
There is a massive amount of actual tech debt on the Tableau monolith side that just can't be overcome without huge investment. Tableau spent years trying to fix that and couldn't make a dent, SF brought an even more short-sighted planning process in and only made it worse.
Granted that Tableau could never fully commit to the efforts and the highest level of executives were only interested in making Tableau an attractive acquisition target. Exception being Francois, who still seems to care about Tableau the product.
Salesforce success is reliant on lack of serious competition. Beyond that it is decades behind modern software engineering practices.
Do you seriously need a third party tool to back up the data in a SaaS application? Astonishing!