I'm a big thrifter - love a good thrift store. I have two semi-close to me, thankfully, but I also thrift online. Like you said, some things...you just don't know how they'll fit. I keep doing dresses and sometimes I don't even know why because it's SO hit and miss to do it online. I remember having a complete meltdown when the pink dress I had ordered online to wear to my friend's funeral (she loved all things pink, something we had in common) didn't fit right, and I had to go to the mall to get one that worked. And I tried on like five before I found the right one.
And yet, I'm sitting here wearing a Thred Up dress and I've gotten five compliments today, lol. So I keep doing it, because I do find those treasures.