The problem of finding the perfect partner doesn't seem so intractable if you recognize it is completely unreasonable to expect one person to satisfy 100% of your needs for 30 years+.
It's expected to be rare, and the searchers don't have the same feeling of single desperation.
Because they are always hunting, they have a high profile.
Other poly people are pretty boring and have pretty normal ideas about love except that they believe (and know) you can love more than one person at a time. Such a person tends to keep a low profile and is going to get confused with bigamists, cheating monogamists, etc.
Thus it is more like cheating among mono people (who also use online dating) which is not exceptionally rare. The difference is that you aren’t cheating.
The poly community isn’t much of a community because there are big moral differences between the participants: unicorn hunters are a running gag but you have many sad couples where somebody was cheating and then forced the other to accept it. If you fly the poly flag you’ll attract a lot of people you don’t want to know so some think it is like ‘Fight Club’.