Y'all are ridiculous. $20 is less than the median hourly wage in the US for both men and women, even worst case scenario you're earning $7.25 an hour so almost 3 hours of work to pay for ad free Sync. I challenge you to make a better app in those same 3 hours so you don't need to pay for it.
Not only are you paying for the app as it is now, you're paying for years if not DECADES of updates too. All done by ONE GUY.
If you don't like it, don't use it. Stop character shaming the dev for trying to make an honest living creating an app a LOT of people (including myself) wanted.
I too dream of a world where we've moved on from capitalism to a socialist utopia like is in the United Federation of Planets, but we are not currently in that world. So until that time, we all have to earn a living to pay our landlords and feed ourselves.
For most things we are given a choice between ads or paying, and I almost always choose paying for no ads as I can't stand them either. But until developers can live without bills and only do work for free because they enjoy it, our choice remains pay for no ads or be served ads. So I paid for no ads.