Using POF and OkCupid in the 2010-2013 time frame was Game on harder mode.
However, most men who did enough volume on POF and OkCupid could get dates. If a man sent 100 messages to women over a weekend on those sites, he'd probably get some responses and some first dates out of it. POF and OkCupid were different because women had to at least see your messages. In the swipe app era, they can swipe left and ignore the man. The man can't even try to make something happen in the inbox in the app era because he can't get there with the left swipe.
There were men who would send copy & paste messages to a lot of women on POF and OkCupid in those days, which was somewhat efficient. Some men would customize some of their messages.
Most men have been in a tougher position on Tinder/Hinge/Bumble than POF/OkCupid.
In 2010-2013, in-person approaching was still a better option than POF/OkCupid.
This description is close to what I'm seeing with the elder Millennials near my own age.
Bumble's format (where the woman has to make the first move) has its pluses. One downside, however, is (as you pointed out) men aren't able to spam broads on Bumble.
In retrospect, my dates from POF and OkCupid were nothing special.
I got 2 dates from an 18 year old on OkCupid when I was 20. She was a nerdy 18 year old with an alternative (bordering on goth) style. In other words, not the type of girl who would be in high demand (that's probably the only reason I was able to get her)
Then when I was 21, I got one date from OkCupid with an obese girl at my college (even though we went to the same college, we didn't know each other until we met on OkCupid). The broad ended up disliking me after the 1st date for reasons totally unknown to me.
Next, after I graduated college, I got an 8 month relationship with a strange fattie from POF who couldn't even fully speak English.
In conclusion, I had to engage in dumpster diving to even get the minimal amount of success I had on OkCupid and POF.
In person approaches got me rejected 100% of the time in college, with the exception of one girl from one of my classes who turned out to be so strange (even by my standards) I had to dump her after a week.