Saying it over and over doesn't make it true. You're wrong.
https://poe.ninja/challenge/builds
This parses only the top ~100,000 builds in terms of their speed to 100 and relative distance to 100 for those that aren't there yet. There are ZERO skills in the game that have 100% representation on a single class. Some come close, but none are 100%. This means that every single skill has at least two options for the class it picks even when picking the simplest, bare minimum, one-dimensional comparison of "reach 100 first", before considering ANY other factor in the game, of which there are hundreds or thousands. Every single skill has players picking multiple classes and being competitive purely from a speed to 100 aspect, before building around survival, or mechanical diversity within a given build archetype, or specializing for the many, many different content types within the game.
Even at the very, very most basic level, what you say is demonstrably and overtly wrong. Every single person in this thread can click the link above, and pick one skill, or one starting class, or one unique, or one talent point, and see the vast and varied builds that use that particular one dimension in different ways. These aren't builds that are just scraping by; they are all fast enough and high enough level to be measured by poeninja. These are all current, active PoE players that have achieved this within the most recent and still active PoE league going on now. Any person who wants to can go today, level up a character, and follow the build of any character on this website and "succeed" in PoE, whatever you measure that as.
Your argument is flatly incorrect. Stop saying it.