The problem is that you can't really make proper use of it.

Yes, there's 24 lanes total. 4 of those are pretty much guaranteed to be dedicated to an M.2 slot, and you're almost certainly using it like that. The other 4 are probably dedicated to a second M.2 slot - although some seem to use it for a NIC or USB controller as well.

That leaves 16 Gen5 lanes intended for the GPU. In practice there aren't any Gen5-capable GPUs out there, so you're running those at Gen4. Luckily Gen4 x16 is plenty, so no need to worry about that.

However, if you want to plug in something like a 25Gbit network card, you have to split that into two x8 slots! Suddenly your GPU gets Gen4x8 - which although usually fine can in some cases impact performance. Want to use a third PCI-E card? It gets split into 8x / x4 / x4, and you suddenly don't have enough bandwidth for that network card - because it only supports Gen2 or Gen3 and really needs all 8 lanes.

So that's still fine, I guess. You can throw in a single decent NIC or HBA or whatever. Not the end of the world. And indeed, the onboard connectivity isn't too shabby for more casual use. But, that's not what I expect from a high-priced top-of-the-line build!

If you're lucky that third PCI-E slot is actually connected to the chipset instead and gets x4 as well - although x2 or even x1 aren't unheard of either. But that means it's now sharing that one Gen4x4 connection with two SSDs, some USB-C controllers, SATA drives, a network card, wifi, and who knows what else. Everything gets attached to the chipset, and it can't provide anything wider than x4. You simply can't attach a 25G NIC to that: that Gen4x4 might have the bandwidth, but a last-gen enterprise NIC requires Gen3x8.

When I'm building a top-of-the-line workstation, I want to run four SSDs in a RAID 10 setup and add a 25G NIC - without two of those SSDs getting the equivalent of a Gen4 x2 if you're lucky. I want to add a NIC and a HBA. I also want to have the option of adding a USB-C expansion card, or a sound card, or a converter for enterprise SSDs, or a video capture card!

So yes, the total bandwidth available from the CPU across all 24+4 lanes is more than enough, but I can't make proper use of it. I'd rather see a chipset with a Gen5x8 uplink, or two chipsets with their own Gen5x4 uplink to the CPU. Beef them up to support some extra downlink lanes, and give them support for x8 links, and they'd actually be useful for workstations.

Until then your only realistic option is a Threadripper board. Something like this isn't even that much more expensive - and it provides six PCI-E Gen5 x16 slots! I don't even care that it has 2x 10G NICS onboard, and 4x Gen5 M.2 slots, and 2x Gen4x4 SlimSAS slots, and 2x 40G USB ports. Even if it were lacking all of that, there'd be pleeenty of expansion slots to add it. That's what I want from a high-end board.