When the ‘last mile’ is copper, the ISPs almost always use xDSL for the data delivery.
The extra equipment increases latency, decreases reliability, and often precludes high upload speeds.
I’m on true full fibre, and I get 500/500mbps, with the option of going to 2.5Gbps. A friend of mine on the same ISP who is limited to ‘fibre to the neighborhood’ maxes out at 300mbps down, 90 up.