The "actual engineering" you are referring to is a $1.00 BMS board.

We are well past the point where we should have standardized batteries. We have bunch of standardized wall outlets that accommodate an array of "non-zero chance of literally killing your users" end products. No reason for battery packs to not be standardized (other than vendor lock in).

I'm sorry but you're dead wrong about the BMS. BMS doesn't address any of the things I listed.

You're also wrong about standardization - standarization at the cell form factor level is correct. Different applications have different capacity vs power density requirements, temperature range requirements, cost, lifecycle... a pouch cell that goes in a drone looks a lot like one that goes in a cell phone but they're optimized for completely different workloads.

Also we already have standardized interfaces for external batteries with most power banks using USB-C, so in a way your wish has already come true.