You're not wrong, I think it's inappropriate if someone attends church just so they can meet someone of the opposite sex, and if someone's scanning the sanctuary during worship looking for a mate rather than doing what he or she is there for (worshiping God) then that's a big slap in the face in my opinion.
That being said, church is a reasonable venue to meet someone because there are a lot of things that happen outside of the church service itself. For example, my church has four services every Sunday, and after each one people filter outside on to this courtyard area adjacent to the sanctuary. They mingle, greet each other, enjoy some coffee, usually the pastor(s) are outside greeting people, and it's a chance to see the folks who normally attend a different service because those who attend the next one are usually on their way in.
I'd be lying if I said I hadn't noticed 1-2 attractive women as I've walked outside after church (at the old traditional service, imagine that! I guess I'm not the only one with that sort of taste). Now I'm not going to run up to one and throw a slap bracelet on her wrist claiming her as my property. But I might introduce myself if I can work up the courage to do so.
To answer your question better, outside of church I've found that I have met people at group events (BBQ's, dinners, birthday parties, even co-ed baby showers...ugh), bars, school and work. There are plenty of venues to meet people in you just have to widen the scope of things that you do. If all you do is go to work, come home, binge on Netflix, and go to bed, you're not giving yourself many opportunities to meet people.
Then there's online dating. I'm not a fan of it at all, but it has worked for a lot of people so I can't say it's a farce. Depending on where you live and the site you're using, it can be pretty effective. I know couples who have met on Tinder, Match.com, OKCupid, eHarmony and even J-Date.
So it starts with considering what you're willing to do and then finding out what works best for you and your area.
