Agree broadly with what you're saying, especially ending industrial animal agriculture and reducing meat consumption.
As you implied, continuing current levels of meat consumption for 8 billion humans, even with regenerative techniques, will still result in substantial increases in land/water use and other negative impacts. We should be sceptical of regenerative grazing claims as well, as they are often pushed by the industry, without sufficient evidence.
I'm hesitant to say just because we've been farming animals for thousands of years is good justification for continuing it (at least at this scale on non-marginal lands). After all, it did lead directly to the problems we face today, as people clung on to traditional methods without thinking even as they migrated and new technologies/knowledge became available. For example, European colonists brought hard-hoofed cows, sheep, goats, horses, and deer to Australia, despite the country's native fauna all being soft-footed, leading to soil compaction and many resultant ecological issues. Now almost 50% of Australia's land surface area is used for red meat farming, and it is the leading cause of deforestation in many parts of the country.
On plant parts that humans can't eat, perhaps it's fine to let wild animals eat them, further improving biodiversity (after all we need a healthy biosphere of many species providing ecosystem services for long-term human survival), or we can compost or process into other products. I'd be looking into stock-free organic farming and precision fermentation as new promising approaches as well.