As a novice, I'm currently studying the designs and work of Dieter Rams and lesser known contemporary studios such as, http://pharusdesign.com/en/case/rio-cello/ , watching them wield their craft has taught me more than any college course ever could. We are very lucky that such work has been preserved for the benefit of future generations.
Design is a deeply collaborative process, with each designer standing on the shoulder of giants. Great design needs to be studied and preserved so that it is accessible in the long-run. So far that has been easy to do. The designs have been on paper, and can be viewed in physical products. But now, with the advent of design tools made entirely for the web, I am worried that many great works will slip through the cracks of history.
In the future, we'll no longer be able to benefit from hindsight. The groundbreaking designs whose impact doesn't become obvious or important until decades into the future might evaporate with time, with little to show for it. After all, will Figma keep all designs, permanently in their archives, even when companies go bust and stop paying their bills? No matter how influential or interesting their design was? Will we be able to do autopsies of work from this era when Figma's servers are down?
Data ownership doesn't seem to be an option in Figma's paradigm. You do not have a copy of the tool, you only execute a part of it. You do not possess the data, they store it for you. Should there be an event where Figma is acquired or goes out of business, then (in all likelihood) every user of this platform will lack the ability and the choice to preserve their work for future generations (and for their business).
What are the odds of Figma staying as it is, in the control of founders, chugging along as a profitable business a year from now? 5 year from now? A decade? Two decades?
This timeline may seem to be long, but the average startup takes 7 years to IPO. Consequently, if you choose Figma as your tool of choice now, then it will be a marriage that lasts a decade or more.
I prefer Sketch and other tools because they store files natively. I know who is in control of my data. And, if need be, I can archive these files and the latest version of the program so that they can be spun up in the future, decades from now, for future generations to view.
Or, in the business context, there is data portability and ownership, when you control your data, you can control how it is inherited by future iterations of your product teams.