Just to reinforce the point, we are about 5km from our exchange. AFAIK the cabling follows the road between us and the exchange.

On ADSL we were connected to the exchange via a cabinet about 1.5km from the house. On a good day we got over 2Mbps download over the 5km of copper.

When VDSL first came to us, we were connected via the same cabinet and would get 12 to 14Mbps download. That would be on fibre as far as the cabinet then the exiting copper infrastructure to the house. Not very good in the overall scheme of things but a dramatic improvement on what we had previously as a result of 3.5km of copper being superseded by fibre.

Then we had another major upgrade with a new All-In-One cabinet installed at the entrance to the village about 250m. from our house. This brought fibre right to that cabinet then the old copper. We now get 75 to 80 Mbps download sync.

Low ADSL speeds are more usually due to distance than the quality of the line.