Earlier quoted context omitted.
I bought a $400 laptop in 2011. Trying to upgrade it in the years after for something at the same price point was an exercise in frustration - when almost every new mobile Intel CPU ended with a "U" and had the computation reduction that came with that.
I think you're fooling yourself. A characteristic 2011 mobile part would have been something like a Core i3-2350M, and a very comparable more recent part would have been the i3-8121U. They both had similar prices at launch, same core and thread count, but the later U-series processor is 2-4x faster depending on application and uses less than half the power.
And yes the CPUs saw improvements at the same component cost, but actually finding a real laptop with even an equivalent CPU inside at the budget end wasn't possible. The laptops got features in some places, but at a cut processor cost. I'm talking about the lower end of the market (the M1 you mentioned is way way wayyy above there) for people who can afford the bare minimum. As you go up in price you get more options, but the low end was noticeably more difficult to purchase in if you weren't looking for the newer features and just wanted the same benchmarks.