I watched it when the first 2 seasons were available on Amazon Prime and caught season 3 ....elsewhere. I liked it a lot. The plot was engaging, the acting was phenomenal (Tatiana Maslany is a goddess) and it was well directed. I'm just sad I was so late to the party. Somehow I still haven't watched the last season. Tbh I'm not sure if I saw season 4 either (but I think I did).
People definitely talked about it though, especially when it first came out. From 2013-2015ish there was a lot of buzz around it; it would trend on Twitter when it was on and popped up on people's top 10 lists all the time. The only thing that changed is that there was a marked decrease in promo in the latter seasons which is normal for many shows, but something that aired on BBC America needed all the help it could get and the show suffered for it. Don't get me wrong, it's still slept on, but a lack of heavy promo didn't help.
I look at Orphan Black like I look at Dollhouse tbh. Both great shows that so many still don't know about or have forgotten.