I feel Buddhism has done fairness to every human being in its teaching.
Most human aspect of Buddhism is it does not say only Buddhists will go to heaven or have a comfortable life after death.It says people who do good, behave good will be rewared in heaven or next life regardless of their religion.
But karma or rebirth concepts are not scientific .We cant see them or prove them.
Same like GOD & heaven.They are not scientific.
But there cant be an eternal life because it is disgusting.religions are based on stimulation of our sensory system.Hell will give you eternal pain.Heaven will give you eternal pleasure.
But scientifically our sensory sytem is formed us to survive & continue our life via reproduction.