Whenever there is a discussion about raid performance, the go-to rebuttal is almost always "play what you want to play", as if it handwaves away the genuine performance concerns that are being raised in the argument. Nonetheless, do raiders really get to play the spec that they want to in raids, especially those specs who are always underperforming?
I can see how there might be some players, who have been veterans in their guilds, can get away with it while the rest of the guild puts up with them due to their authority. But for the majority of players, particularly those who are joining a new guild, I don't believe they have the luxury of truly "playing what they want".
If we look at the warcraftlogs statistics, the general trend is that the lower the DPS, the lower the total number of parses. For example, the bottom 10 specs have a total of 17,838 total parses whereas the top 10 specs have a total of 54,698 parses, more than 3x as many. This indicates to me that players aren't really playing "what they want", but playing "what is best".
Based on the above, can we really say that raiders are playing "what they want"?