They're comparing these applications to older applications that loaded instantly on much slower computers.
Both sides are right.
There is a ton of waste and bloat and inefficiency. But there's also a ton of stuff that genuinely does demand more memory and CPU. An incomplete list:
- Higher DPI displays use intrinsically more memory and CPU to paint and rasterize. My monitor's pixel array uses 4-6X more memory than my late 90s PC had in the entire machine.
- Better font rendering is the same.
- Today's UIs support Unicode, right to left text, accessibility features, different themes (dark/light at a minimum), dynamic scaling, animations, etc. A modern GUI engine is similar in difficulty to a modern game engine.
- Encryption everywhere means that protocols are no longer just opening a TCP connection but require negotiation of state and running ciphers.
- The Web is an incredibly rich presentation platform that comes with the overhead of an incredibly rich presentation platform. It's like PostScript meets a GUI library meets a small OS meets a document markup layer meets...
- The data sets we deal with today are often a lot larger.
- Some of what we've had to do to get 1000X performance itself demands more overhead: multiple cores, multiple threads, 64 bit addressing, sophisticated MMUs, multiple levels of cache, and memory layouts optimized for performance over compactness. Those older machines were single threaded machines with much more minimal OSes, memory managers, etc.
- More memory means more data structure overhead to manage that memory.
- Larger disks also demand larger structures to manage them, and modern filesystems have all kinds of useful features like journaling and snapshots that also add overhead.
... and so on.