>The whole linux stack got bigger though - just look at what you need now to compile stuff, cmake, meson/ninja, mesa, llvm and so forth

Those are all development tools. Has the runtime overhead grown proportionally, and what accounts for the extra weight?

Runtime-wise we use more garbage collected languages now. Java and such are great and can be very high performance, the real cost though is memory. GC languages need much more memory for book keeping, but they also need much more memory to be performant. Realistically, a Java app needs 10x the amount of memory as a similar C++ application to get good performance. That's because GC languages only perform well when most of their heap is unused.

As a side-note, that's how GC languages can perform so well in benchmarks. If you run benchmarks that generate huge amounts of garbage or consistently run the heap at 90%+ usage, that's when you'll see that orders of magnitude slowdown.

Oh also containers, lots more containerized applications on modern Linux desktops.