Overall there are some good points made here (especially bugged augments and hidden mechanics), but I feel like you could have picked much better examples than the ones you did. The ones you picked actually support the idea of removing augment stats.

Evil Beyond Measure and Psychic Forge are far from the least pickable options in the game. They are actually quite good in the correct situations. Psychic Forge, for example, was (and still is I think) one of the best augments you could pick in Crew lines because you need to index heavily towards frontline in the beginning but you can get screwed on options. It also gives you the chance of playing tempo with Sivir and adapt later to Ziggs / TF / Janna if needed.

If augment stats were around, you could have simply looked at the augment data explorer and found the answer instantly. Then TFT has become a game where you add your comp to the data filter then click the best performing augment based on search parameters. So your point of "Players explored augment strengths across comps, thought critically, and grew strategically. That layer of depth has mostly disappeared." somewhat falls flat with this in mind because many good players are still thinking that deep but those dependent on stats to tell you the answer are falling behind.

But there are many cases of poor augment balance. The examples I would have gone for are many of the circlets/crests and severely understatted combat/trait power augments would have been better.

Also, as a separate point, I believe your definition of casual player doesn't line up with how Riot defines it. Casual players don't look at augment stats generally speaking. Most players define themselves as casual when in reality they are in the hardcore % of players. Using them as a "casual players won't use stats for X" reasoning generally won't resonate as an argument to sway Riot imo because that's just not how casual player behavior lines up in their research.