Java was designed to make manual memory management a non-concern. Yet, ironically, it's the runtime that require more explicit memory tuning than any others.

It absolutely doesn't need any memory tuning whatsoever. People just read 2 decades old blog posts and apply whatever random flag they see.

For 90% of workflows you don't add any command line arguments, for the remaining 10% you may specify a heap size. That's all.

This does not match my experience. The amount of manual tuning needed for memory management in C/C++ (which Java was designed to improve upon) was orders of magnitude greater than with Java just to get it correct, let alone efficient in terms of memory usage and performance.