During F4 design the thinking was that missiles were the way forward - longer range and guided. But pilots in Vietnam soon found themselves in close combat, inside the range of the missiles or in situations were their shots were very low pk. They needed a gun. The Lightning was a victim of the same thinking and, remember, the original concept was a rapid reaction to the Soviet high level bomber threat - get up there fast, shoot missiles, come home (usually single engine).
Multi role aircraft still had some use for strafe until the ground threat and better weapons moved aircraft higher and away from the threat. But again the brains soon discovered that they had thrown away a great tool.
The debate went on, in fact it still does. In my time at 1 Group and the AWC, there were plenty (mainly mud-movers) who questioned the need for guns on fighters, asking when was the last time anyone was shot down with a gun?
We almost lost it from Typhoon, but that was more politics and the potential damage the gun would do to the airframe due to the use of composites - fortunately some better thinkers came along and CofG came to our aid.
Lots of people would like to overlook the amazing results from the A-10 because it's a hard one to argue against. When they say they don't need it in F-35, they mean it won't fit, it would lose the weight-loss program, it would ruin stealth and, anyway, who would put such an expensive aircraft so close to a ground threat. Of course it's invisible so it would really be OK.
Is the RAF anti-gun? Well, some are and others will gladly sacrifice the gun for other stuff where mass and space are issues.
You can't jam bullets.