I've mostly seen the opposite. People whose social lives were centered around dating and meeting people through that, who then settled down, and now don't know how to make just "friend" friends.
Would the two have the same root cause? That's an interesting question - many claim that "tech" (in the abstract, or in the specific eg "facebook likes") are responsible for both, but I don't really buy it.
I don't know what historical rate information we have, but there have always been some loners. They have an easier-to-access platform today, does that skew our perception?
I suspect the lack of pair bonding and childbirth is driving the majority of the reported loneliness.
To some extent modern culture has presented us this model of single-family homes and strongly coupled people against the world, and certainly it might minimize loneliness for the strong couples, but does it maximize loneliness for everyone else?
There's a lot to wonder if we've lost something in losing some of the classic "village model" of multiple families and individuals all in close proximity and relationship to each other in multi-family homes. Especially when you start to include individuals that for one reason or another don't "fit" into more traditional "Hollywood" couple relationship roles (asexual and/or aromantic folks don't always fit neatly into a strongly-bound couple role, as one obvious example to me; differently abled people have other challenges; etc).
Furthermore, a focus on strong coupling discounts the network effects of looser coupling. You may not feel hardly lonely at all always having your significant other around, but that may only be a "local maximum" state. Your maximal happiness may rely on both the reliability of a tight couple and a network of other friends filling other relationship needs. The long tail of strong couple problems from active therapy needs to cheating and divorce rates seems to suggest that it very much could be a local maximum "trap".
Anecdotally, I do feel like an individual that can't win in a game of strong coupling, and it does irk me that the suggestion is simply "be part of a couple". Hollywood and dating companies throw a lot of money at trying to tell people like me that this is the only solution, and it certainly seems like it's not a (workable) solution at all.