Trying to go back to the original spirit of the thread, I have a bit of a hard time accessing Federer's results under Annacone.
@Jelenafan's stats above cannot be dismissed, that is, if you look at Federer post 2008, what happened under Annacone is "average" in the sense that it has some highs as well as some lows. You cannot dismiss the Wimbledon win, but on the other hand Federer will always be a threat there and there is an aspect of "randomness" in each win. Was Federer much better in 2012 Wimbledon than in 2014 Wimbledon? Hard to tell. Yes, there were moments of absolute brilliance in his 2012 win over Murray, but had he won in 2014 we (Federer fans) would simply have seen the highlights of that final 24324 times more, and found out tons of moments of brilliance as well. In the end, we always judge entire time spans based on what happened on the course of 5 minutes (in this case, the last five minutes of the 2014 Wimbledon final).
Tennis is simply way too mental to make an assessment based on pure results -- specially if you are trying to differentiate between similar results (and, yes, runner up and champion are similar results. Before you scream, compare it to champion and R1 loss). A guy can simply be playing at a general higher level and fail to execute at the key moments (compare Federer Wimbledon finals from 2018 and 2019, for example).
So, in a nutshell, I don't think the results from Annacone's years are different enough from the average to serve as an indicator in either direction. You must try to analyze what you see in court (as subjective as it may be) to get a conclusion -- and that is why I like the "spirit"of this thread. The part that I don't like about it is using Nadal as barometer. I mean, if Federer hired Annacone with an eye in Nadal, then yes, it was the dumbest move of all time, but frankly speaking this is not 2006/2007 anymore, any decision based on his Nadal match up at that point would be idiotic in the first place, for more than one reason that I won't list here.
I do remember watching Federer play during those days and having a feeling that something was pretty wrong (yes, that is as subjective as it gets). There were things I liked -- some renewed attacking spirit -- but the game as a whole seemed, well, unbalanced. In a way that was expected, you could see that he was being actually coached -- not following his instincts, but that felt strange anyway.
Edberg's days seemed a step forward, maybe Edberg's virtue was to find a way harmonize some directions given earlier by Annacone with Federer's natural instincts. It was surely waaaay nicer to watch Federer play under Edberg than under Annacone -- of course some exceptions along the way.
The larger frame notwithstanding, in hindsight it all seemed like the necessary steps for him to reach his post 2017 level. In one of my extremely rare moments of rest in these last two months, I found myself in front of the TV one sunday morning and they were showing the AO 2017 final. There is no doubt that the shot that won that match was the back hand -- simply way too many rallies that the bh stood firm, not to mention the winners. But the willingness to come forward was there, and that you can trace back to Annacone. Yes, Federer always has been an wonderful net player, but pre Annacone (specially if you look at post 2008), he lost that fluid ability to suddenly find himself at the net -- and then after that it was Annacone that added add those "artificial" charges forward that some people still don't like, but I really see the point in those. Edberg further polished an already marvelous net game, but the net attacks as a "plan" rather than a natural reaction (or a desperate move) are from Annacone -- and that was surely a contributing factor to the 2017 AO win -- a few key points were won just forcing Nadal to try a difficult pass.
In other words, I don't wish he never hired the guy, I just wish he left him sooner.