You can't solve all (FS) problems for all people simultaneously. Custom FS solutions by Apple (recently), Oracle (20 years ago), and countless other vendors in the last 3 decades are about choosing different trade-offs, learning from mistakes, and growing the technology with the hardware (fat-12 -> fat-16 -> fat-32 was all about growing with increasing drive size). But if you truly believe that nothing substantial has been gained, why did you bother upgrading to btrfs?
Older filesystems suffered from a variety of problems that could and did ruin data for a lot of people. Modern filesystems like NTFS5, ZFS, btrfs, etc., make their best effort to ensure data can actually be consistently read and written, which while being outside of the most common path of reading non-fragmented files sequentially (I'd even say 99.99% of actual IO in non-server configurations), it is still a use-case that is important for the vast majority of computer users. You know, people who do business, homework, take pictures, ...
On the GC side of things, the Azul VM has shown to be quite effective at addressing many of the performance issues with garbage collection in Java (which gets even better when you stop doing stupid crap in Java). And there are garbage collected languages that are not Java that don't suffer the same stuttering problem of the Java GC (that have also been around for 20+ years, and have steadily gotten better over time).
You can't solve all (FS) problems for all people simultaneously. Custom FS solutions by Apple (recently), Oracle (20 years ago), and countless other vendors in the last 3 decades are about choosing different trade-offs, learning from mistakes, and growing the technology with the hardware (fat-12 -> fat-16 -> fat-32 was all about growing with increasing drive size). But if you truly believe that nothing substantial has been gained, why did you bother upgrading to btrfs?
Older filesystems suffered from a variety of problems that could and did ruin data for a lot of people. Modern filesystems like NTFS5, ZFS, btrfs, etc., make their best effort to ensure data can actually be consistently read and written, which while being outside of the most common path of reading non-fragmented files sequentially (I'd even say 99.99% of actual IO in non-server configurations), it is still a use-case that is important for the vast majority of computer users. You know, people who do business, homework, take pictures, ...
On the GC side of things, the Azul VM has shown to be quite effective at addressing many of the performance issues with garbage collection in Java (which gets even better when you stop doing stupid crap in Java). And there are garbage collected languages that are not Java that don't suffer the same stuttering problem of the Java GC (that have also been around for 20+ years, and have steadily gotten better over time).