ISP-provided router/modem combos silently use outdated WiFi chipsets

Over 70% of US broadband subscribers use the router/modem combo (gateway) provided by their ISP, typically paying $10-15/month in rental fees. These devices often ship with WiFi 5 (802.11ac) chipsets even when the customer is paying for gigabit plans, throttling wireless speeds to 300-400 Mbps. So what? Customers paying $80-100/month for gigabit service only get 30-40% of their paid speed over WiFi, which is how 95%+ of their devices connect. So what? They call tech support blaming the ISP for slow speeds, wasting hours in support queues. So what? The ISP blames the customer's devices or runs a speedtest over Ethernet that shows full speed, gaslighting the customer into thinking the problem is on their end. So what? Customers either overpay indefinitely for speed they can never use wirelessly, or they buy their own router AND keep paying the rental fee because many ISPs make it difficult to return the gateway. This persists because ISPs profit from rental fees ($120-180/year per customer) and have no incentive to upgrade hardware that technically 'works,' and because the FCC's broadband speed requirements are measured at the modem, not over WiFi.