OkCupid was based on knowledge and attitudes as well, using a type of machine-assisted learning that deduced what people really find important to know about each other. Rather than what someone designing a questionaire assumes. And rather than people relying on looks, impulsive attraction, and random early conversations where people are winging it.
The central idea, in addition to free-form profiles, was users submitted a lot of answers to multiple-choice questions, as well as the answers they would like a potential match to have (because they might be different), and how important each answer was to them. So this worked well for people who were looking for attributes that complemented theirs, in addition to other attributes where similarity was what mattered.
In addition, users could submit questions, and over time the system grew to mainly ask those questions that were found to be statistically useful in matching people up.
This meant great questions for matching would rise to the top of the pool, while poor questions, or badly written ones, or unhelpfully ambiguous ones, would not.
This also meant that the kinds of things people ended up matching on were more diverse than any other site. So it really helped people find matches on non-mainstream attributes that mattered to them personally, that were not generally reflected on other sites (such as match.com...). Things like how much do you like your partner to dress as a goth, do you mind if your partner sleeps with other people too, and if not what about cuddling others without sex, not just what's your orientation, but effectively what subtle aspects of orientation that haven't been formally enumerated, does it bother you if your partner supports a particular type of politics, what about bedtimes, what is your approach to raising children (smack or never smack), do you like drugs and if so what kind, etc. Basically anything you can think of which humans actually care about.
It was an excellent way to find people that shared your attitudes and worldview, especially if you had non-mainstream interests.
Tinder will give you none of that.
I used the old OkCupid for years and met a few new friends through it.
It tended to match me up with people already in my "friends of friends" extended circles, with good quality common interests and attitudes, and was great for expanding those circles. I thought it was one of the best sites on the net for getting to know new people. (Way better than, say, Facebook, where you exchange comments but never really get to know new people one-on-one.)
And with people I already knew, we would have fun checking out how well OkCupid thought we matched up.
I want back a couple of years ago, after a few years break, and OkCupid had removed everything that made it useful before. I mean everything. It just wasn't any use. Sadness.
Never been back since.
It's a shame there's nothing else on the net like the old OkCupid. It was socially useful and unique.
Hopefully someone will come along and replicate the good parts in a new site someday.