Can we not have a PCIe card that's ASIC (and isn't GPU) with even DDR 4 or DDR 5 memory (Let's say 128 GB) onboard and being able to shove four of them on a consumer grade motherboard and then being utilized in parallel?

Noob question.

DDR4 or 5 would really run into bandwidth and value issues.

Bandwidth on that memory interface and setup for dual channel would be significantly worse than Strix Halo, which already exists and could be an entire compute setup with no need for an ASIC.