Meta Sr. Software Engineer interview questions

Facebook emailed me often asking me to interview for a position there, and I finally did after I was ready to leave my job. I had an initial call with a recruiter who just gave me generic information. She then scheduled a technical interview for me, and I took 2 weeks to prepare. I did the interview on CoderPad over their video service. The interviewer didn't have the best grasp of English, so it was difficult for me to follow what they were asking. She asked me to do a simple algorithm implementation. I tried asking questions about what the expectations were for the work, and much of the time, she had difficulty explaining what she was asking, and would get flustered and realize she explained something wrong and have to walk it back. Once I got a good grasp on the conditions and the edge cases, I set about writing out the algorithm. There was no expectation for it to actually run, so I walked her through my logic. She didn't really say much, and changed the input and asked how that would change the output and I walked her through again. She then asked me for the Big(O) of the algorithm, and I gave her my answer - which I believe was correct. Nothing was said afterwards - I'm used to interviewers asking how I could have improved the algorithm. She left me about 3 minutes for questions for her, and that was it. Overall, it was not a great experience. These interviews in general seem geared towards kids right out of college, and not testing the abilities of someone with over 15 years of experience (me). I emailed the recruiter afterwards asking about next steps, and she said she'd get back to me the next week. Got a generic rejection email on Monday. I emailed asking for feedback as I was surprised, and was ignored. I sent my solution to 5 friends who are senior/principle engineers, and all of them said they have no idea why I was rejected. I've interviewed and worked at other prestigious tech organizations, and never had an experience like this before. I'm not sure what sort of candidate they're looking to attract with this experience, but I certainly would never entertain interviewing for a job there again.