Can you provide a link that says mainstream Hinduism has abandoned this belief in caste?
Hinduism doesn't believe in caste; the caste system is a pan South-Asian cultural thing.
Can I prove that the birth based caste system that befalls South Asia today and is often associated with Hinduism is not actually the Hindu concept of varṇa -- which is often incorrectly interpreted to mean the same as caste (it isn't)? Then yes, yes I can.
I can prove this through Hindu scripture (Ṛgveda, the oldest of Hindu scriptures), "
I am a bard, my father is a physician, my mother's job is to grind the corn" (Sanskrit: कारुरहं ततो भिषगुपलप्रक्षिणी नना
(Rigveda Book 9 Hymn 112 Verse 3) which proves there is no -- I can also prove that there is no concept of "untouchable" caste in the same way -- "
The four-fold order was created by Me"
Bhagavad Gita 4:13: the four castes in question are Brāhmaṇa (Brahmin) -- the priests, doctors and teachers, Kṣatriya -- the warriors and politicians, Vaiśya -- the storekeepers, merchants and artisans, and Śūdra -- the farmers and labourers. No Dalits; no untouchables.
I can also prove it through history: there are stories of people being born as one "caste" and becoming another, such as the sage Viśvāmitra.
In short: the varṇa was simply to "play to your strengths". Not everyone wants to be a warrior or a teacher, and one's life -- including duties -- change accordingly.
I'm not saying the Israelites were killing them based on what they knew about their past sins. I'm saying that was the reason why they were providentially set up to be killed. The Israelites weren't told this necessarily, they may have had the idea that this was their fate, but it wasn't the immediate reason for the annihilation of the tribes in question.
But it still asks why children should be killed.
That's for another thread. [snip for space]
Indeed, that is worthy of its own whole thread.