Perhaps roads are getting too busy to share with selfish private car drivers making unnecessary car journeys and taking driving two abreast (generally single person car journeys, no passengers). I ride a lot in London where it will be common to overtake hundreds of cars in minutes... now who is slowing down the roads - the cyclists or the car drivers?
How many parents drive their kids less than 1 mile to school in a huge 4x4? Far too many. It's ridiculous.
Cycle lanes almost definitely not fit for purpose. Most are shared use and have driveways / junctions every 5 seconds. Chances are drivers coming out of driveways and junctions will not look so you end up having to cycle along at 10mph just in case. Also there's further challenges - avoiding the pedestrians, dogs not on leads, on retractable leads, glass, debris, and then... BAM the cycle lane just suddenly finishes after 20 yards but the council don't care. They've ticked the "Cycle provision" box!
Check the cycle lanes in Central London. Segregated from traffic, check how many cyclists use those. Thousands a day, because they're good.
I'm curious. How did you define yourself as a cyclist? How often do you cycle?
Some of them aren't fit for cars let alone bicycles.
This is advisable, because idiotic drivers will come along and give you zero room. Then you at least have a bit of breathing room to move left. Why should it matter even if you're in the centre of the road? Drivers are supposed to give at least 1.5m of space.
Thin country roads with a wide cycle path? Hmm.
Where are the mountains in London? Do you also drive a huge SUV round London?