"Cheap mechanics requiring significant investment to actually perform." Quite the oxymoron if I've ever seen one.
Cheap in the sense that they are basically just exploits
I don't see how that detracts from their legitimacy. Why should people not be rewarded for acquiring a better understanding of how the game works? Should my thousands of hours going through jump maps in TF2 not allow me to lord over the people who have not devoted the same amount of effort?
Because they are exploits and unintended mechanics. It is the fastest way I can think of to lose the userbase of a multiplayer game.
Why does their presence being intended or not have an impact there? And how is it an exploit if it's the logical end result of the physics engine?
Because it eliminates mass amounts of a userbase. If you have an exploit that takes hundreds of hours of practice to use correctly, but it gives you a major advantage, you'll stop seeing new players or even average players. You'll be left with the tryhards who do nothing but the exploit.
Halo 2 was absolutely like this. Once you got to a certain rank and certain point in time, it was nothing but exploits and cheaters. And I was one of those that perpetuated it. I could superbounce on all the maps and easily kill entire times with no deaths myself. People would ragequit.
Again, these skills were not exploits. They were game design decisions originally made in QWTF and once valve hired the QWTF mod team to make TFC they kept these same designs while adding new skills.
The ONLY skill that was borderline exploit territory was chophopping, which was banned in competitive play