We're probably still a few years off from being able to switch to this fast I/O yet. With the new game consoles switching over to PCIe SSDs I expect the price of NVMe drives to drop over the next few years until they're cheap enough that the majority of computers are running NVMe drives.
Even with SATA drives like mine though, there's really not that much performance loss from doing IO operations. I've run my OS with 8GiB of SSD swap in active use during debugging and while the stutters are annoying and distracting, the computer didn't grind to a halt like it would with spinning rust. Storage speed has increased massively in the last five years, for the love of god fellow developers, please make use of it when you can!
That said, deferring IO until you're done still makes sense for some consumer applications because cheap laptops are still being sold with hard drives and those devices are probably the minimum requirement you'll be serving.