What makes a support better then another support?

I've always loved support. I've played supports in whatever form in most games and I've learned as much as I can to be the best possible support I can in any given situation. What I don't love is an adc telling me the support I'm going to use is garbage ( apparently are garbage) or better calling me garbage for picking it. This has happened on multiple occasions, and its becoming frustrating because, in a normal match where you can't see what the enemy is picking, I've actually had adc's leave games because they don't like the support i picked in comparison to the enemy team's (thankfully this hasn't happened yet in ranked, probably because there's the opportunity to change what support is picked). This makes it so hard for me to get anywhere in terms of gaining IP for more supp champs or runes (got my eyes on at the moment).

So I must ask, and this is directed at you adc players, what makes a support better then another to you? What, for example, would make Blitz inferior to Thresh, (which many people tell me is an amazing support whose stood the test of multiple nerfs, but quite frankly I don't see it). If both champions can get you kills and protect your adc, then what's the problem with either of them? I don't really play adc so I don't know the mindset that those players are in. And if your wondering, I've directed my question at you guys because its usually just been the adc who cares. Top, mid, jgs really haven't gotten onto my choice of support (which makes sense since they aren't going to be laning with me). I want to know so I can improve my chances of winning not only in lane, but the round as a whole. The only thing more frustrating then having a hard game is having an adc be even harder on you for choosing a "garbage" support and calling gg. Because if there is anyone people love blaming, its the support. Any input is welcome.