Where do you add more storage after you've used your 1-2 nvme slots and the m.2?
I would think an SSD is going to be better than a spinning disc even with the limits of sata if you want to archive things or work with larger data or whatever
Only SATA made it common for motherboards or adapters to support more than 2-4 hard drives. We're back to what we used to do before SATA: when you're out of space you replace the smallest drive with something larger.
There are SATA SSD enclosures for M.2 drives. Those are cheap enough now that granny can still upgrade her old PC on the cheap.
pcie expansion cards? SATA isn’t free and takes away from having potentially more PCIE lanes, so the only real difference here is the connector
PCIE expansion card with m2 slots?
(SSDs are "fine", just playing devil's advocate.)
Counterpoint: who needs that much fast storage?
4 M.2 NVMe drives is quite doable, and you can put 8TB drives in each. There are very few people who need more than 32TB of fast data access, who aren't going to invest in enterprise hardware instead.
Pre-hype, for bulk storage SSDs are around $70/TB, whereas spinning drives are around $17/TB. Are you really willing to pay that much more for slightly higher speeds on that once-per-month access to archived data?
In reality you're probably going to end up with a 4TB NVMe drive or two for working data, and a bunch of 20TB+ spinning drives for your data archive.