They used to accept the accountant's data file produced by QuickBooks, but only if the QB version was no older than three years.
This is part of the "Quickbooks Pro Advisor" agreement they signed. If you passed their silly tests and want to advertise using this "qualification", you have to agree not to work with files produced by software older than 3 years, their official support window. I don't know how strictly this is enforced by Intuit, but I suspect it isn't since my own accountant is breaking this agreement by working with my QBDT2019 files, and they haven't yet tried to get me to upgrade.
I suspect
@Sky-Knight is correct that this will eventually push accountants to support other softwares so THEY don't erode their SMB client base, but that change won't be immediate. I have about 6 small accounting firms as clients, and so far they are either "go Quickbooks or go home" or "you can use what you want but we charge more for non-Quickbooks users". I know this because I have discussed this whole thing with them individually over the last couple of years as this writing has been on the wall for a while. So far, none of them have said they are going to change their stance, but that probably won't happen until their own market starts to shrink.
BTW, the fees for accountants have gone up as well - they aren't happy about it, but it is just the cost of doing business, so you know what that means, they are passing the cost along to the clients - as they should. Intuit knows this, of course - this is what happens when monopolies exist...I don't know why I should think otherwise.
For my own company, I use Intuit Online Payroll through my accountant's subscription - they bundle the cost of this into my quarterly fees (which are fixed and haven't increased in a few years now - I'm waiting for that shoe to drop). They do my payroll taxes & filings, my year-end closing calculations & entries and my year-end personal and business taxes. I've looked at moving to a different payroll solution a couple of times and it seems clear I am getting a pretty good deal where I am, so I've stayed.