fade "talking bollocks".......
Unlike BA or Virgin you do not "join' Norwegian, you join an employer agency. Your services are rented to Norwegian similar to contracted cleaning staff.
Although you may indeed wait years for upgrade at BA or Virgin, you will gain seniority, pension, benefits and, most importantly, have all the employment law, labor rights and labor principles of a direct employment relationship. Notwithstanding, union representation and collective agreement with your airline employer.
On upgrading: "everyone who is eligible will get their chance"
Does your agency employment contract provide for any seniority system with the lessee airline, Norwegian? - Answer: No it does not.
"I seriously hope our selection process is still working"
Is that the selection process which assesses if the applicant has enough funds to pay for their training?