IPv6 was designed under assumptions of bus-based local networks that Ethernet switches rendered obsolete, a foundational error that perpetuates adoption, security, and scalability problems in contemporary internet architecture. Pennarun (2017) details how early LANs like ARCNET with 8-bit jumper-set addresses and broadcast domains shaped IPv6 features including SLAAC (RFC 4862), link-local addressing (RFC 4291), and Neighbor Discovery (RFC 4861), diverging sharply from IPv4's simpler extension as the source notes IETF participants still defend these as elegant. This lens reveals the protocol was optimized for a pre-switch world of shared wires where layer 2 and layer 3 boundaries blurred. Original coverage praising IPv6 address exhaustion fixes missed IPv4's effective NAT adaptations (RFC 1631, RFC 3022) and carrier-grade NAT deployments; APNIC data tracked by Huston (2022) shows IPv4 sharing techniques sustaining growth post-IANA exhaustion while IPv6 global adoption lingered near 35% in 2022 per Google and APNIC stats, patterns the source implies but does not quantify. The bus-era focus overlooked how switched point-to-point topologies reduced need for IPv6's multicast-heavy autoconfiguration. Synthesizing Pennarun (2017), Huston's APNIC reports on transition metrics (apnic.net, 2018-2023), and IPv6 core spec (RFC 8200), the design's end-to-end assumptions clash with middlebox reality, inflating routing tables despite hierarchy claims and complicating security via device exposure that requires stricter firewalls than IPv4 NAT provided; these persistent challenges trace to 1990s IETF decisions that failed to anticipate switched Ethernet dominance and policy-driven address sharing.