Bit of a tangent, but: it’s absolutely possible to learn a relatively simple card-counting system and play with positive expected value in a casino. You can easily run simulations to prove this.
I think this reinforces the GPs point. It's not all that hard to learn some basic card counting but probably 99% of people who try it casually end up playing a -EV game, due to the fact that the edge is very small and requires practicing/playing with much more discipline than most people want to bother with.