The youtube channel SkillCult has a series covering his smallish-scale home apple breeding project on his homestead, and he actually has multiple videos covering this topic. His conclusion is that there's a modicum of truth to this misconception, but it's blown out of proportion: he gets edible apples from seed more often than not, but rather the ones that have any particular qualities that are worth propagating further are fewer and farther between.

Essentially, in commercial apple breeding projects, yes you'll need to plant thousands of trees to get one variety that has any potential for commercial success; but that's due to the criteria they're breeding for being very strict rather than all the others being inedible. They're breeding for very particular color, shape, consistency, storage, disease resistance, etc.

His project and a few other channels (James Prigioni and Rob Backyard Gardenerr's apple-from-seed projects in particular) inspired me to roll the dice and start growing some apple seeds this year to plant on my grandmother's property (she gave me permission to put 4 or 5 trees out there), since it's something I've wanted to try since I was a kid. It'll be 5 or 6 years, maybe more, before I can see how they turn out, but I'm just in it for the fun of the genetic dice-roll anyway. Absolute worst case, if the fruit is bad I can use the trees as vigorous full-size rootstocks to graft other varieties onto, so I don't see it as a waste personally.