“What did the Romans ever do for us?
… All right, but apart from the sanitation, the medicine, education, wine, public order, irrigation, roads, a fresh water system, and public health”
Replace “Romans” with “Increased RAM usage”.
Sure you could strip away a lot of that functionality, even at the distribution level (by for example not using an init system at all, instead just one shell script to initialize things), but then you'd end up with an operating system that's not general purpose for today's standards anymore.
Windows 95 also didn't do things the modern way. It didn't keep an image of every application's windows in RAM. It kept track of what covered up what, and then asked applications to redraw themselves when needed.
Another huge amount is going to features like internationalization. Unicode is a beast that takes a good amount of code to implement, and Arial Unicode is a ~20 MB TTF file.
Modern luxuries like being able to tweet in Japanese are quite expensive.