The problem is that there's a fine line between "not being a jerk" and "playing support 90% of the time"
In ranked, I used to always let people play what they wanted, and filled whatever was open all the time. As a result, I ended up playing support a ridiculous amount.
Pick order is the way that nice people get to play what they want sometimes.
A better way to handle it would be to kindly let your team know that you've been playing a lot of support lately and you would like mid, top, jungle or adc (while in the back of your mind telling yourself you'll settle for support if they truly don't give you anything else). Try asking your team if anyone will support or maybe offer to rage bot lane with them as adc. A lot of the times you'll get that person who feeds off of your confidence and will take support for you.
If not, just gauge the situation, if you feel you can grab the role you want and trust your team will fill and not troll...do it. No harm in honestly being selfish, it's just when you make a habit of it and start being negative about it that makes it a problem.