Maybe macros in excess aren't such a problem(within reasonable ranges) but Micros clearly are and that has not been published, oh what a uproar from EI fanboys if that became proven.
I agree with much of what you have been saying, but a blanket statement like above is why the factions were at war a few years back. You weren't here, but it was a bloody battle. Some were banned for life because it got so out of control.
At the time of the micro tox wars, most everyone was dosing CSM+B. Most likely that was the root of most problems. First is the type of iron used vs tank pH. Next is the nature of CSM+B itself, which is produced in huge vats to spread over crops.
Now let's just take B itself. I have tested various B levels and in my tank it has the narrowest effective range. Not enough is not good, and too much can be toxic. I tested the upper end and the reaction was swift and certain. So let's take a vat of CSM+B, then scoop out the pound you purchase, then scoop out the 1/16th or 1/32nd tsp most were using. What are the odds of the B in that fractional tsp to be in the correct range? IMO very, very slim.
And we could on and on with each individual micro. Some of these are a minute physical amount. Getting the same from dose to dose using CSM+B is highly unlikely.
To compound matters further EI dosing was listed as 0.5 Fe from CSM+B 3 times a week. That amount was way too high for most tanks, and could itself cause problems. It wasn't that long ago that Barr relented and the calculators brought it down to 0.2 x 3 times per week. Zorfox still has it as 0.5.
So yes, micros can cause toxicity. I believe much can be attributed to crummy micros, and some to flat out too high of guidelines. In general it's a more nuanced argument than simply stating micros are toxic.
And I actually don't know of too many EI fanboys around anymore. I started with EI, and found quickly that it was not the best dosing for my tank. It's taken years of experimenting to get to my current dosing, and I am still tweaking and searching for the optimal amounts. It's funny those guys are still at war with EI, yet few that I know are dosing EI.
I've been enjoying following your journey, and I think there are things to be learned there. Healthy debate and experimentation is good for the hobby. But it seems you may be buying in to a dogma with which you have no practical experience. No different than an EI fanboy who enters the hobby and preaches what he has not experienced. Just saying you may want to give things more time and see actual results in your tank before offering broad conclusions.
Heck, I have doing this for almost 4 years, and I don't have many broad conclusions. All I really know is what happens in my particular tank, and that's really all the perspective I can provide.
Last thing is that I would beware of folks performing micro experiments on a single species in a bare bottom tank. IMO, the only thing it proves is what happened with that particular set of parameters in that particular tank. Extrapolating that to another tank with a different set of everything is tricky business.
Good luck and I am very much looking forward to seeing what the next chapter brings.