If you note I said sure it made sense to concentrate on the more urban areas first but as part of the license for 4G, 5G etc.. technology the operators had to expand coverage to 95% of the population. Sure the more rural areas might have to wait longer but they wouldn't be left out.
The reality is, basically everyone has electricity, telephones and roads, so eventually basically everyone will have reasonably capable internet. The infrastructure just has to catch up.
As you correctly stated, the mobile industry is pushing 4G and 5G when it hasn't rolled out 3G properly yet. BT has no incentive whatsoever to put fibres out to villages in Cornwall, and the government schemes have really just turned into BT slush funds.
Multiple screw ups and issues, but the inevitable should happen, eventually...