Varnashrama is not a man-made system but refers to natural classifications that appear to various degrees in all human societies.
Individuals have different innate tendencies for work and exhibit a variety of personal qualities.
There are also natural phases in life when it is easier and more rewarding to perform certain activities.
Hinduism teaches that individuals best realise their potential by taking into account such natural arrangements and that society should be structured and organised accordingly.
Each varna and ashram has its own specified dharma. What may be desirable for one section of society may be degrading for another.
For example, absolute non-violence, which includes refraining from animal sacrifice, is essential for the priestly class but considered wholly unworthy of a Kshatriya (warrior).
Generating wealth and producing children are essential for householders, but intimate contact with money and women is spiritually suicidal for the renunciate.
Underlying all these apparent differences is the common goal of advancing in spiritual life based on sanatana-dharma.
Without the spiritual equality and sense of service inherent in sanatanadharma, varnashrama-dharma tends to degrade into a rigid and exploitative caste system.