If you look at the actual generated tax forms, there's a lot of extra pomp around filling out some pretty trivial forms and worksheets. If they cut the desktop software I think I will just move to something like https://www.freetaxusa.com/.
TurboTax occupies a middle ground and it saves me enormous amounts of time.
I eventually decided to abandon them a couple years after they started forcing me to buy some ultra premium pro edition because I had a small amount of "business income." Switched to Credit Karma Taxes, which Intuit then bought, but miraculously some regulator forced them to divest that product, which landed at Cash App. So I have used that (now called Cash App Taxes) since then. It's a free product and even supports business income and state taxes (IIRC, state e-filing was always an additional add-on with TT). It was a little annoying to have to re-enter more that first year, but it's done a good job of rolling forward, and not that I've ever needed it, but they also have that "Audit Defense" thing included for free, another add-on upcharge TT offered.
Their desktop version seems like a webapp embedded inside browser frame; I don't understand why they can't make it available on the web.
So I'm surprised they even still have a desktop version (...presumably not just some electron wrapper). And given how it works, I'd guess most of your data isn't staying local for much of this.
Was it fast? No. Just fast enough. That's why I doubt the desktop app is really any different. They must have a bunch of API endpoints, and the 'slowness' is all on the backend.