It sounds like a paradox that there would be simultaneous epidemics of loneliness and and standoffishness but they cause each other. In one direction the cause is obvious, in the other lack of socialization causes people's "calibration" to go off as their learned tolerance to unexpected things fades. Real social interactions involve a lot of imperfection and what you sometimes see is that without being desensitized, lonely people's standards can be unreachable. (Other commenters have alluded to this being a result of hyper stimulation on TikTok but it predates it.)
Yes, because adults in general have less time to spend with friends than someone who's younger, more mobile (live downtown vs the suburbs) and has fewer responsibilities.
But loneliness is up among all generations, including those who are in the right time and right place (post-secondary). Many reasons for this as well, including the impact of internet and social media. People are less willing to give others a chance because Tinder/Tiktok/IG has trained them to think that another more interesting experience could be right around the corner.