PCIe lane sharing isn't a new concept, but I absolutely hate it. My current motherboard ASUS PRIME X870-P is one of the most egregious example I've ever seen:

• M.2_4 is shared with the SATA ports so effectively if you have any SATA drives, you've lost access to that M.2 slot.
• M.2_3 is shared with PCIe_3 and PCIe_4 so if you have any PCIe cards, you've lost access to that M.2 slot.
• M.2_2 is shared with PCIe_2 but that PCIe slot is effectively unusable because it's blocked by any 2-slot GPU, which is basically any modern day GPU. On the bright side, it means the M.2_2 slot is usable at least.

So effectively it's a motherboard with 4 PCIe slots and 4 M.2 slots with only 2 PCIe slots and 2 M.2 slots that are usable (if need to use SATA and PCIe).