Nearly 5-6 rounds of interview, including telephonic, 2-3 rounds of technical rounds, manager, hr and CEO round

Received a call from Recruiter, discussed about the job profile and scheduled f2f interview. There were 3 technical rounds in f2f interview, next day scheduled for Senior Manager round, and then director round. After all these they mentioned I'm not suitable due to job hopping. Atleast they could have decided not to shortlist because of instability and would not have called for interview. But after clearing all the rounds its bad to say this reason. Overall negative experience.