DS found it pretty awful. Applicants are usually A* kids, used to doing well academically, and choosing which courses to apply for are often the first major decisions of their adult lives.
Rejection first time out is hard. Made worse when your friends are starting to make plans for next year. (Exacerbated, no doubt by the uncertainty and chaos of the pandemic.)
DS, possibly like Nancy's DC was advised to apply for Cambridge/UCL/Warwick/LSE and though he was capable of getting a place at any, it was equally possible that he was rejected by all. As I said on another thread, one of his classmates received four rejections but was accepted by Cambridge (not LSE) the following year. The difference between acceptance and rejection can be tiny.
In retrospect I think it was good that he had his first major disappointments when he was still at home. The school picked up that he was finding it tough and were supportive. He was lucky and eventually got his place, but had he gone elsewhere, or had to take a gap year he would still have been fine. And perhaps this knowledge helped him with later rejections (internships, jobs etc.)
LSE was a good fit for him, though possibly not for everyone. The wait was awful, and I confess that I was not displeased when he decided not to apply to Cambridge, UCL or Warwick at Masters level, because, apparently, their courses weren't as strong, and then chose LSE over Oxford.
Then DD decided to apply for medicine, and we had it all over again. She applied in October and her interviews were not till March.
Again fingers crossed!