I believe referrals are no longer effective because people get referrals pretty easily from fishbowl, online platforms without actually knowing the person. This makes the referral pool similar to regular pool, given the less conversion ratio because of this, companies have started taking referrals with less priority as compared to earlier times.
The kind of actual referral that works when someone would personally speak to hiring manager and put a good word for you. Which i think is actually referring someone.
The concept of referrals via fishbowl, etc due to greed of referral bonus has caused this mode of recruitment almost useless or less effective.
However one should keep on trying with referrals as it might just work sometime.
Rest, i guess best effective method is to use connects, explore and understand open roles in companies you are targeting and then reaching out to HRs and hiring managers on LinkedIn to further explore and get an interview.