Side point (& I'm not the person you were responding to), but I have to ask: Do you not see online dating in the same vein as most other online corporate sites that commodify their users and devalue them for profits?
I personally think online dating is a "meat market" or "horse show" for everyone of every gender & orientation. There's little to no real effort on behalf of these sites to actually increase the number of connections (e.g. via coming up with features that actually encourage making connections), instead their entire ecosystem is designed to encourage the same type of "doom scrolling" that sites like FB encourage so that you stay on their sites/apps for longer viewing ads for longer, or shell out more & more money for their "premium" offerings.
It's hard to deny that online dating does not provide avenues for diversity in presenting people's strengths. Some people are more appealing in person than they are in text for example. Some people aren't photogenic (even if they are actually physically attractive), some people are livelier or funnier in person than they will ever appear in an online dating ad, some people just don't know how to create "eye catching" dating ads....etc.
It doesn't mean there's anything wrong with those people at all, it just means those sites don't provide avenues for their strengths, which is a problem because people are extremely diverse, but instead these sites create the "meat market" dynamic because it's the only thing they apparently know how to do & it increases their profits to do so.
This piece from the Atlantic back in 2016 touched on what I mean:
Moira Weigel is a historian & author of the recent book Labor of Love, in which she chronicles how dating has always been difficult, & always been in flux. But there is something “historically new” about our current era, she says. “Dating has always been work,” she says. “But what’s ironic is that more of the work now is not actually around the interaction that you have with a person, it’s around the selection process, & the process of self-presentation. That does feel different than before.”
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“The thing with design is, at risk of belaboring the obvious, how all of these apps make money is by keeping people on the app,” Weigel says. “Yes, there’s better & worse design, but there is ultimately this conflict of interest between the user of the app & the designer of the app.”
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But getting as many people in front of your eyeballs as fast as possible doesn’t end up saving time at all. “I have women saying that they spend 10 to 15 hours a week online dating, because that’s how much work goes into producing one date,” Wood says.
So if there’s a fundamental problem with dating apps, one baked into their very nature, it is this: They facilitate our culture’s worst impulses for efficiency in the arena where we most need to resist those impulses. Research has shown that people who you aren’t necessarily attracted to at first sight, can become attractive to you over time, as you get to know them better. Evaluating someone’s fitness as a partner within the span of a single date—or a single swipe—eliminates this possibility.
I don't really give a shit how Incels perceive dating (seriously, no one is "owed" sex), but it's hard to deny that online dating sites, like several other online "experiences", have not negatively impacted their "space" for profits, similar to how sites like Reddit & Facebook were supposedly supposed to "help people communicate & make & keep connections" & only became more & more enshittified to improve corporate bottom lines, resulting in the opposite outcome (E.G. Shit like FB heavily encourages divisiveness instead cause that's what gets the ad views, news sites resort to click bait instead of actually reporting news cause again, profits..etc.).
Of course paywalled dating sites might be better on this, but considering the financial status of a lot of people (especially the younger demographics that are having a harder & harder time even finding the time & money to pursue relationships as one of your sources pointed out, which is also a HUGE part of the problem IMO), it makes sense why many would assume the freemium sites are representative of online dating as a whole (since they do have a larger market share as well)
& of course there are some efforts to address the issues I've listed (like Swan)
I don't know for sure since I'm not a sociologist nor have I personally dug deep enough into this topic, but I imagine that while not the sole reason, these for profit dating sites definitely have a sizable impact on the rise of incel "culture".