The lack of feedback from interviews is definitely one of the most frustrating parts. But remember that the success rate for onsite interviews is around 20-50%

The lack of feedback from interviews is definitely one of the most frustrating parts. But remember that the success rate for onsite interviews is around 20-50% depending on company (companies don't publish this stat, but see for instance https://www.quora.com/How-many-people-who-take-the-Google-onsite-interviews-end-up-getting-the-job https://www.quora.com/How-many-people-who-take-the-Google-on...). Even if you had a success rate of around 50%, you would fail 7 onsite interviews around 1% of the time - which is unlikely, but unlikely things do happen. So my advice would be to keep trying - getting 7 onsite interviews is a good sign. Also try to figure out what areas of interviewing did not go well and improve on those areas.